Stirling engine systems, apparatus and methods

ABSTRACT

Systems, methods, and apparatus relating to the use of Stirling engine technology to convert heat, such as from solar radiation, to mechanical work or electricity. Apparatus, systems, components, and methods relating to energy converting apparatus are described herein. In one aspect, the invention relates to the field alignment of panels and the assembly of a concentrator. In another aspect, a passive balancer is used in combination with a ring frame and other moving masses to reduce engine forces and vibration on the structure of the energy converting apparatus while maintaining properly constrained alignment of various suspended masses. In yet another aspect, the invention relates to various over-insolation control and management strategy to prevent overheating of the energy converting apparatus or components and subsystems thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/578,554, filed on Oct. 13, 2009, which claims priority to and thebenefit of U.S. Provisional Application No. 61/104,915, filed Oct. 13,2008, and U.S. Provisional Application No. 61/196,042, filed Oct. 13,2008, the entire disclosures of each of which are hereby incorporated byreference herein for all purposes.

FIELD OF THE INVENTION

The invention relates generally to the field of energy convertingdevices such as Stirling engines. Specifically, the invention relates todevices, systems, subsystems, components and methods that facilitate thecollection and conversion of solar and other types of energy.

BACKGROUND OF THE INVENTION

Current photovoltaic-based systems are expensive to produce and takefrom one to twenty years to generate the amount of power required fortheir own production. Accordingly, a need exists for other energyconverting technologies that are competitive with or otherwise superiorto photovoltaic-based approaches.

SUMMARY OF THE INVENTION

The present invention provides energy converting apparatuses such asStirling machines or engines and related components, methods,apparatuses, and systems with advantageous assembly, heat exchange,manufacturing, fast mirror alignment, over insolation control, vibrationcontrol, ring frames, receiver assembly, assembly tools, thermal zoneisolation, face plates, and other properties and features. As a result,there are many novel apparatuses and methods disclosed herein thatrelate to heat exchange, device protection, vibration control, and otherfeatures to adapt the Stirling cycle to solar power generation.

In one embodiment, the invention relates to a mechanical assembly thatincludes a solar energy collector, typically a reflective surface or anarray of mirrors, and an energy converting apparatus. In one embodiment,the energy converting apparatus includes a Stirling cycle engine. Afree-piston Stirling engine embodiment can be configured such that boththe collector and the energy converting apparatus are elevated relativeto the ground on a pier to enable better solar energy collection andengine positioning.

One embodiment provides a system for converting solar energy intoelectricity. The system can include: a solar energy concentratorincluding a non-planar front surface including plurality of panelsdefining the non-planar front surface, each panel including a pluralityof edges; a boom; and an energy converting apparatus. The energyconverting apparatus can include an incident solar energy receivingsurface aligned to receive solar energy reflected from the solar energyconcentrator; a ring frame including a plurality of supporting membersand a top substantially circular region including an outer circumferenceand an inner circumference and including a plurality of attachmentmounts; and an engine disposed within an engine housing suspended withinthe inner circumference and substantially perpendicular to the topsubstantially circular region, the boom connecting and aligning theenergy converting apparatus and the solar energy concentrator. In someembodiments, the concentrator has a focal point positioned at a pointoffset relative to the incident solar energy receiving surface.

In some embodiments, the system includes a temperature sensor positionedto detect temperature changes in the incident solar energy receivingsurface. In some embodiments, the system includes a drive unit connectedto the solar energy concentrator and the temperature sensor, the driveunit programmed to misalign the concentrator with a source of solarenergy and reduce an amount of solar energy impinging on the incidentsolar energy receiving surface when the temperature measured by thetemperature sensor exceeds a predetermined threshold.

In some embodiments, each panel includes a non-planar surface, whereinthe non-planar surface includes a first portion including a first edgeand a second edge, the first and second edges being radially orientedwith respect to the center of the concave reflector when the panel ispositioned in the concave reflector; wherein the non-planar surfacecomprises a second portion including a third edge and a fourth edge, thethird and fourth edges are radially oriented with respect to a secondcenter that is nonconcentric with the center of the concave reflectorwhen the panel is positioned in the concave reflector; and wherein whenassembled in the concave reflector, the concave reflector includes aslot, running to the circumference of the reflector from substantiallythe center of the reflector, the slot having parallel edges.

In some embodiments, n panels comprise the plurality of panels, whereinn is an integer greater than two, the panels arranged such that anon-planar concave dish is formed from the arrangement of the n panels,the non-planar concave dish defining a star shaped hole and the slotformed from a plurality of edges of the n panels, the n panels aresubstantially identical in shape.

In some embodiments, the concave dish is oversized to provide excesssolar energy relative to a relative maximum amount of solar energy thatthe energy converting apparatus can tolerate before overheating.

In some embodiments, each of the plurality of attachment mounts aresubstantially perpendicular to the top substantially circular region.

In some embodiments, the system includes an elongate slew plateconnected to the outer circumference of the substantially circularregion, the elongate slew plate defining an attachment point for acover, the cover sized to substantially surround the energy convertingapparatus while leaving the incident solar energy receiving surfaceexposed to receive solar energy.

In some embodiments, the system includes a vibration transmissionreduction system for reducing the transmission of vibrations between theengine housing and a frame. The system can include: a plurality ofisolation springs, each isolation spring forms a circular mount withinwhich is positioned the engine housing, the circular mount is attachedto the frame; and a passive balancer attached to the engine housing. Insome embodiments, the plurality of isolation springs are arranged toform a cylindrical mounting structure having a longitudinal axis. Insome embodiments, the engine and the passive balancer are aligned alongthe longitudinal axis or an axis parallel to the longitudinal axis. Insome embodiments, the axial spring stiffness of the isolation springs isselected in response to the gravity load so as to ensure the enginehousing remains in a predetermined axial tolerance band. In someembodiments, the predetermined axial tolerance band range from about 0mm to about 0.6 mm. In some embodiments, the circular mount is attachedto the ring frame. In some embodiments, the frame is a ring frameincluding a plurality of supporting members and a top substantiallycircular region, wherein the isolation springs are flexures, wherein theengine housing and passive balancer are suspended by the flexures.

In some embodiments, the concentrator includes a chassis, and thechassis includes a first mating surface and a second mating surface,both mating surfaces sandwiching a plurality of elongate members whichradiate outward from a common center, each of the plurality of panelsattached to at least one elongate member. In some embodiments, thesystem includes a biaxial drive assembly supported by a pier andconnected to the chassis. In some embodiments, the biaxial driveassembly is configured for causing rotation of the concentrator abouttwo orthogonal axes. The biaxial drive assembly can include: a firstdrive unit having a first axis of rotation; and a second drive unithaving a second axis of rotation and offset from the first drive unit,the second drive unit is positioned separate from first drive unit suchthat the first and second axes of rotation are orthogonal but do notintersect. In some embodiments, the first and second drives cause thechassis to move, the first drive unit causes rotation of the chassisabout a vertical axis of rotation of the first drive unit; the seconddrive unit causes rotation of the chassis about a horizontal axis ofrotation of the second drive unit, and when the second drive unit hascaused a rotation of the chassis about the horizontal axis of the seconddrive unit so as to cause the directional axis of the chassis to bevertical, the directional axis of the chassis is parallel to butnon-coincident with vertical axis of rotation of the first drive unit.In some embodiments, the first axis is an azimuth axis that is offsetfrom the second axis, the second axis is an elevation axis. In someembodiments, wherein the azimuth axis is normal to level ground andconfigured to move an object based on compass direction. In someembodiments, at least two of the plurality of edges define a slot.

One embodiment provides a panel for use in a substantially concavereflector. The panel can include a non-planar surface, wherein thenon-planar surface has a first portion including a first edge and asecond edge, the first and second edges being radially oriented withrespect to the center of the concave reflector when the panel ispositioned in the concave reflector, wherein the non-planar surface hasa second portion including a third edge and a fourth edge, the third andfourth edges not radially oriented with respect to the center of theconcave reflector when the panel is positioned in the concave reflector;and wherein when assembled in the concave reflector, the concavereflector includes a slot, running to the circumference of the reflectorfrom substantially the center of the reflector, the slot having paralleledges. In some embodiments, the panel further includes a rear surfaceand wherein the rear surface includes a plurality of attachment bosses,each attachment boss capable of being attached to an elongate member ofthe conclave reflector to thereby form the concave reflector having apredetermined focal point. In some embodiments, a substantially circularregion defining a first hole and a plurality of triangular shapedregions defining a plurality of holes are formed when the concavereflector is assembled. In some embodiments, the slot defines a firstarea substantially equal to a second area defined the first hole andplurality of holes. In some embodiments, the panel includes a structuralsubstrate, a top surface including a reflective surface, and a bottomsurface including a plurality of attachment bosses, the attachmentbosses disposed such that the panel can be attached to at least oneelongate member. In some embodiments, the reflective surface includes aplurality of tiles. In some embodiments, the elongate member includes arib.

One embodiment provides a panel for use in a substantially concavereflector. The panel can include a non-planar surface, the surfacedefining a sector of the concave reflector, the non-planar surfaceincluding a first edge and a second edge, the first edge and second edgeradially oriented relative to a first center; the non-planar surfaceincluding a third edge and a fourth edge, the third edge and the fourthedge radially oriented relative to a second center. In some embodiments,the orientation of each of the edges is such that when a plurality ofthe panels are arranged to form a concave reflector a slot is defined inthe concave reflector.

One embodiment provides a kit for forming a concave reflector. The kitcan include: a plurality of elongate members; and a plurality of panels.Each panel can include: a non-planar surface, wherein the non-planarsurface includes a first portion including a first edge and a secondedge, the first and second edges being radially oriented with respect tothe center of the concave reflector when the panel is positioned in theconcave reflector, wherein the non-planar surface includes a secondportion including a third edge and a fourth edge, the third and fourthedges are radially oriented with respect to a second center that isnonconcentric with the center of the concave reflector when the panel ispositioned in the concave reflector; and wherein when assembled in theconcave reflector, the concave reflector includes a slot, running to thecircumference of the reflector from substantially the center of thereflector, the slot having parallel edges.

One embodiment provides a solar energy concentrator. The concentratorcan include n panel segments, wherein n is an integer greater than two,the panel segments arranged such that a non-planar concave dish isformed from the arrangement of the n panel segments, the non-planarconcave dish defining a star shaped hole and a slot formed from aplurality of edges of the n panel segments.

One embodiment provides an alignment tool for use in assembling aconcave reflector, where the concave reflector can include a hub plate,the hub plate including a first alignment point, and a plurality ofelongate members, each of the plurality of elongate members including ahub end for attachment to the hub and a distal end, the distal endincluding a second alignment point. The alignment tool can include anelongate body portion including a first end and a second end; a firstattachment unit located at the first end of the elongate body portion;and a second attachment unit located at the second end of the elongatebody portion, wherein the first attachment unit is for attaching thealignment tool to the first alignment point on the hub plate, and thesecond attachment unit for attaching the alignment tool to the secondalignment point of the elongate member to thereby align each elongatemember with respect to the hub plate prior to fixation of the elongatemember to the hub plate.

One embodiment provides a method of assembling a reflector unitincluding: a hub plate, the hub plate including a first alignment point;a plurality of elongate members, each of the plurality of elongatemembers including a hub end for attachment to the hub plate and a distalend, the distal end including a second alignment point; and a pluralityof panels. The method of assembly uses an alignment tool which includesan elongate body portion including a first end and a second end; a firstattachment unit located at the first end of the elongate body portion;and a second attachment unit located at the second end of the elongatebody portion. The method can include the steps of: attaching an elongatemember to the hub plate; attaching the first attachment unit of thealignment tool to one first alignment point on the hub plate; attachingthe second attachment unit of the alignment tool to the second alignmentpoint of the elongate member; aligning the elongate member with respectto the hub plate; fixing elongate member to the hub plate; repeatingeach step for each elongate member of the plurality of elongate members;once the elongate members have been affixed to the hub plate, affixingeach of the plurality of panels to the elongate members.

One embodiment provides a method of assembling a collector having acentral axis for use with an energy converting apparatus. The method caninclude the steps of sandwiching a plurality of elongate members betweena first substantially planar mating surface and a second substantiallyplanar mating surface, each elongate, member including two substantiallycollinear pins located on either side of a first end of each elongatemember, each mating surface defining a plurality holes, each hole sizedto receive one of the pins; and securing the substantially planar matingsurfaces such that the collinear pins are positioned withincorresponding holes in each respective mating surface such that themating surfaces are perpendicular to the central axis and a second endof each of the structural members radiates outward away from the centralaxis. In some embodiments, the method can include the step of attachinga plurality of panel segments to the plurality of elongate members. Insome embodiments, each panel segment includes attachment bosses on afirst side and a reflective surface on a second side. In someembodiments, the method can include the step of aligning all of thepanel segments to form a collector focus point at a location above thecollector. In some embodiments, the alignment step is performed bysequentially tightening a plurality of fastener elements positioned toattach the panels to the elongate members by a prescribed amount.

One embodiment provides a drive assembly for causing rotation about twoorthogonal axes. The drive assembly can include: a first drive unithaving a first axis of rotation; and a second drive unit having a secondaxis of rotation, wherein the second drive unit is positioned separatefrom first drive unit such that the first and second axes of rotationare orthogonal but do not intersect. In some embodiments, the first andsecond drives cause a body having a directional axis to rotate, thefirst drive unit causes rotation of the body about a vertical axis ofrotation of the first drive unit; the second drive unit causes rotationof the body about a horizontal axis of rotation of the second driveunit, wherein when the second drive unit has caused a rotation of thebody about the horizontal axis of the second drive unit so as to causethe directional axis of the body to be vertical, the directional axis ofthe body is parallel to but non-coincident with vertical axis ofrotation of the first drive unit. In some embodiments, the first axis isan azimuth axis that is offset from the second axis, the second axis isan elevation axis. In some embodiments, the azimuth axis is normal tolevel ground and configured to move an object based on compassdirection. In some embodiments, the elevation axis is configured to movean object through a plurality of elevations. In some embodiments, theelevation axis is arranged relative to the azimuth such that a topsurface of the first drive unit is defines a hole through which cablingcan be routed. In some embodiments, the first drive unit has a firstorigin and a first coordinate system and wherein the second drive unithas a second origin and a second coordinate system such that the firstorigin and the second origin are offset relative to each other.

One embodiment provides a pier assembly for supporting a two axisrotatable object. The pier assembly can include: a base; a hollowelongate member extending from the base; and a drive assembly forcausing rotation of the object about two orthogonal axes. The driveassembly can include: a first drive unit having a first axis ofrotation; and a second drive unit having a second axis of rotation,wherein the second drive unit is positioned separate from first driveunit such that the first and second axes of rotation are orthogonal andoffset relative to each other such that each axis does not intersect theother. In some embodiments, the first drive unit includes a surfacedefining a hole that connects to the hollow elongate member. In someembodiments, the hole is sized to receive a wire or cable.

One embodiment provides a vibration transmission reduction system forreducing the transmission of vibrations between an engine housing and aframe. The system can include: a plurality of isolation springs, eachisolation spring forms a circular mount within which is positioned theengine housing, the circular mount is attached to the frame; and apassive balancer attached to the engine housing. In some embodiments,the plurality of isolation springs are arranged to form a cylindricalmounting structure having a longitudinal axis. In some embodiments, thesystem can include a heater head, engine, and passive balancer arrangedalong a common longitudinal axis, the engine disposed within the enginehousing. In some embodiments, the axial spring stiffness of theisolation springs is selected in response to the gravity load so as toensure the engine housing remains in a predetermined axial toleranceband. In some embodiments, the predetermined axial tolerance band rangesfrom about 0 mm to about 0.6 mm. In some embodiments, the frame is aring frame including a plurality of supporting members and a topsubstantially circular region. In some embodiments, the circular mountis attached to the ring frame. In some embodiments, the frame is a ringframe including a plurality of supporting members and a topsubstantially circular region, wherein the isolation springs areflexures, wherein the engine housing, heater head and passive balancerare suspended by the flexures. In some embodiments, the engine housing,heater head and passive balancer are suspended by the ring frame andmaintained in collinear alignment using the circular mount.

One embodiment provides a method for reducing over-insolation of a heatexchanger. The method can include the steps of: providing a heatexchanger having a surface area for absorbing solar radiation;concentrating solar radiation on the surface area of the heat exchangersuch that the concentrated solar radiation impinges on a portion of theentire surface area of the heat exchanger; and moving the concentratedsolar radiation about the surface area of the heat exchanger. In someembodiments, the step of moving the concentrated solar radiationincludes moving the concentrated solar radiation in a pattern. In someembodiments, the pattern is substantially circular. In some embodiments,the solar radiation is moved about the surface at about 1 to about 30revolutions per minute. In some embodiments, the step of moving theconcentrated solar radiation includes randomized movement of theconcentrated solar radiation. In some embodiments, concentrated lightimpinges on less than about 100% of the entire surface area of the heatexchanger. In some embodiments, the method can include the step ofreducing the portion of the surface area onto which concentrated solarradiation impinges when the temperature of the heat exchanger reaches apredetermined limit, thereby reducing thermal input. In someembodiments, the method can include the step of providing a solarconcentrator or components thereof. In some embodiments, the method caninclude the step of providing a Stirling engine. In some embodiments,the Stirling engine is configured to be in thermal communication withthe heat exchanger. In some embodiments, the heat exchanger is inthermal communication with an energy converting apparatus, the energyconverting apparatus selected from the group consisting of a chemicalenergy conversion device, a thermal energy storage device, a gasturbine, a multi-cylinder engine, a multi-piston engine, a steamturbine, a steam power tower, a fuel cell, and a water-based energygeneration systems.

One embodiment provides a method for extending the use-life of a solarheat exchanger. The method can include the steps of: providing a solarconcentrator; providing a heat exchanger; providing an aperture betweenthe heat exchanger and the solar concentrator: directing a concentratedbeam of the solar radiation from the solar concentrator, through theaperture; and when the temperature of the heat exchanger reaches apredetermined limit, reducing the amount of solar radiation which passesthrough the aperture, thereby reducing the amount of solar radiationimpinging on the heat exchanger. In some embodiments, the solarconcentrator is a reflective dish. In some embodiments, the step ofreducing the amount of solar radiation includes misaligning the solarconcentrator and the aperture.

One embodiment provides a method for reducing over-insolation of a heatexchanger. The method can include the steps of: providing a solarconcentrator; providing a Stirling engine; providing a heat exchangerhaving a surface area, the heat exchanger being in thermal communicationwith the Stirling engine; providing an aperture between the heatexchanger and the solar concentrator; aligning the solar concentratorand the aperture such that a fraction of the solar radiation from thesolar concentrator passes through the aperture, wherein the fraction ofsolar radiation impinges on a portion of the surface area of the heatexchanger; and moving the solar radiation about the surface area of theheat exchanger. In some embodiments, the method includes the step ofreducing the portion of the surface area onto which concentrated solarradiation impinges when the temperature of the heat exchanger reaches apredetermined limit, thereby reducing thermal input. In someembodiments, the method includes the step of moving the concentratedsolar radiation such that substantially no concentrated solar radiationimpinges on the heat exchanger when a predetermined maximum temperature,power, pressure, swept volume, resistance, current, or position, isreached.

One embodiment provides a method for using an over-sized solarconcentrator. The method can include the steps of: providing anover-sized solar concentrator; providing a heat exchanger; providing anaperture between the heat exchanger and the over-sized solarconcentrator; during non-peak solar conditions, directing substantiallyall of the solar radiation from the solar concentrator through theaperture; and during peak solar conditions, reducing the amount of solarradiation which passes through the aperture and moving the solarradiation about the surface area of the heat exchanger, thereby reducingthermal input. In some embodiments, the over-sized solar concentrator iscapable of producing about 3 kW_(e) when solar insolation is about 850W/m². In some embodiments, the over-sized concentrator is capable ofproducing about 10W_(e) when solar insolation is about 100 W/m². In someembodiments, the method includes the step of providing a Stirlingengine. In some embodiments, the Stirling engine is configured to be inthermal communication with the heat exchanger. In some embodiments, theover-sized solar concentrator is capable of concentrating more solarradiation than can be thermally processed by the heat exchanger orStirling engine.

One embodiment provides an apparatus which can include: a Stirlingengine; a heat exchanger in communication with the Stirling engine; asolar concentrator for concentrating solar energy onto the heatexchanger; and an aperture between the solar concentrator and the heatexchanger for controlling the amount of solar energy which reaches theheat exchanger. In some embodiments, the solar concentrator is a dish.In some embodiments, the dish has a reflective surface. In someembodiments, the apparatus includes a housing for shielding the Stirlingengine from the concentrated solar energy. In some embodiments, at leasta portion of the housing is configured to reduce thermal or solarabsorbance. In some embodiments, a thermal spray is applied to thehousing.

One embodiment provides a method for extending the use-life of a solarheat exchanger. The method can include the steps of: providing a solarconcentrator; providing a heat exchanger; providing an electromagneticradiation path between the heat exchanger and the solar concentrator;directing most of the solar radiation from the solar concentrator alongthe electromagnetic radiation path; and reducing the amount of solarradiation impinging on the heat exchanger in response to sensorfeedback. In some embodiments, the method includes the step of reducingthe rate at which the heat exchanger heats. In some embodiments, themethod includes the step of moving the concentrated solar radiationabout the surface area of the heat exchanger.

One embodiment provides a method for using an over-sized solarconcentrator. The method can include the steps of: providing anover-sized solar concentrator; providing a heat exchanger; providing anelectromagnetic radiation path between the heat exchanger and theover-sized solar concentrator; during non-peak solar conditions,directing most of the solar radiation from the solar concentratorthrough the electromagnetic radiation path; and during peak solarconditions, reducing the amount of solar radiation which passes throughthe electromagnetic radiation path and moving the solar radiation aboutthe surface area of the heat exchanger, thereby reducing thermal input,spreading hot spots, reducing the rate at which the heat exchangerheats, and/or maintaining coolant temperature.

One embodiment provides a method for improving performance of an energyconverter system. The method can include the steps of: providing a heatexchanger having a surface area for absorbing thermal energy;concentrating thermal energy on a portion of the surface area of theheat exchanger, and moving the concentrated thermal energy about thesurface area of the heat exchanger, thereby reducing thermal input,spreading hot spots, reducing the rate at which the heat exchangerheats, and/or maintaining coolant temperature.

In general, various details and dimensions relating to an energyconverting apparatus system are provided below. Although in onepreferred embodiment the systems described below relate to a 3 kilowattenergy converting apparatus whereby solar energy is converted toelectrical power, the embodiments and dimensions thereof describedherein are not intended to be limiting, but are provided to beillustrative examples.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention can be better understood withreference to the drawings described below, and the claims. The drawingsare not necessarily to scale, emphasis instead generally being placedupon illustrating the principles of the invention. In the drawings, likenumerals are used to indicate like parts throughout the various views.The drawings associated with the disclosure are addressed on anindividual basis within the disclosure as they are introduced.

FIGS. 1A and 1B are schematic diagrams illustrating a system forconverting solar energy into electricity, mechanical work, thermalenergy, or chemical energy, in accordance with an illustrativeembodiment of the invention.

FIG. 1C is a schematic diagram illustrating an energy convertingapparatus, in accordance with an illustrative embodiment of theinvention.

FIG. 1D is a schematic diagram of a frame with a top slew plate (heatshield), in accordance with an illustrative embodiment of the invention.

FIG. 1E is a diagram of an assembled energy converting apparatus, inaccordance with an illustrative embodiment of the invention.

FIGS. 2A and 2B are interior views of energy converting apparatuses,FIG. 2B showing an interior view of the engine and related components,in accordance with an illustrative embodiment of the invention.

FIGS. 2C to 2F are schematic diagrams depicting receiver assemblies andcomponents for the same, in accordance with an illustrative embodimentof the invention.

FIGS. 3A to 3J are various schematic diagrams illustrating exemplaryreceiver assemblies and components for the same, in accordance with anillustrative embodiment of the invention.

FIG. 4 is a schematic diagram illustrating a system, in accordance withan illustrative embodiment of the invention.

FIGS. 5A and 5B are schematic diagrams depicting a system in a stowposition, in accordance with an illustrative embodiment of theinvention.

FIG. 6 is a schematic diagram illustrating a system, in accordance withan illustrative embodiment of the invention.

FIGS. 7A to 7N are schematic diagrams illustrating an exemplary boom,chassis, and components for the same, in accordance with an illustrativeembodiment of the invention.

FIG. 8 is a schematic diagram illustrating an alignment tool, inaccordance with an illustrative embodiment of the invention.

FIGS. 9A to 9F are schematic diagrams illustrating exemplary chassiscomponents, in accordance with an illustrative embodiment of theinvention.

FIG. 10 is a schematic diagram illustrating a drive unit, in accordancewith an illustrative embodiment of the invention.

FIGS. 11A to 11D are schematic diagrams illustrating a panel segment, inaccordance with an illustrative embodiment of the invention.

FIGS. 12A to 12B are schematic diagrams illustrating a collector dishand collector dish assembly, respectively, in accordance with anillustrative embodiment of the invention.

FIG. 13 is a schematic diagram illustrating a panel segment, inaccordance with an illustrative embodiment of the invention.

FIG. 14 is a schematic diagram illustrating the underside of a panelsegment, in accordance with an illustrative embodiment of the invention.

FIGS. 15A to 15D are schematic diagrams illustrating collector dishassembly hardware, in accordance with an illustrative embodiment of theinvention.

FIG. 16 is a schematic diagram illustrating a panel arm attached to apanel segment, in accordance with an illustrative embodiment of theinvention.

FIGS. 17A to 17C are schematic diagrams illustrating solar energypassing through a receiver assembly and impinging on a heater head, inaccordance with an illustrative embodiment of the invention.

FIG. 18A is a schematic diagram of a circular mounting ring, flexuresprings, a heater head and other components of an energy convertingapparatus, in accordance with an illustrative embodiment of theinvention.

FIG. 18B is a schematic diagram of a flexure spring used to reduceengine vibrations, in accordance with an illustrative embodiment of theinvention.

FIGS. 18C to 18D are schematic diagrams of a ring frame, in accordancewith an illustrative embodiment of the invention.

FIGS. 19A to 19C are schematic diagrams depicting a frame and apparatusassembly, in accordance with an illustrative embodiment of theinvention.

FIG. 20 is a schematic diagram of a heater head, in accordance with anillustrative embodiment of the invention.

FIGS. 21A to 21C are schematic diagrams depicting a top view, a bottomview, and a cross-sectional view of an assembled heater head, inaccordance with an illustrative embodiment of the invention.

FIG. 22 is a schematic diagram depicting a cross-sectional view of aheater head, in accordance with an illustrative embodiment of theinvention.

FIG. 23 is a schematic diagram depicting a channel plate, in accordancewith an illustrative embodiment of the invention.

FIG. 24 is a schematic diagram depicting a flow distributor plate, inaccordance with an illustrative embodiment of the invention.

DETAILED DESCRIPTION

The following description refers to the accompanying drawings thatillustrate certain embodiments of the present invention. Otherembodiments are possible and modifications may be made to theembodiments without departing from the spirit and scope of theinvention. Therefore, the following detailed description is not meant tolimit the present invention, rather the scope of the present inventionis defined by the claims.

The use of sections or headings in the application is not meant to limitthe invention each section and heading can apply to any aspect,embodiment, or feature of the invention.

It should be understood that the order of the steps of the methods ofthe invention is immaterial so long as the invention remains operable.Moreover, two or more steps may be conducted simultaneously or in adifferent order than recited herein unless otherwise specified.

Where a range or list of values is provided, each intervening valuebetween the upper and lower limits of that range or list of values isindividually contemplated and is encompassed within the invention as ifeach value were specifically enumerated herein. In addition, smallerranges between and including the upper and lower limits of a given rangeare contemplated and encompassed within the invention. The listing ofexemplary values or ranges is not a disclaimer of other values or rangesbetween and including the upper and lower limits of a given range.

It should be understood that the terms “a,” “an,” and “the” mean “one ormore,” unless expressly specified otherwise.

The foregoing, and other features and advantages of the invention, aswell as the invention itself, will be more fully understood from thedescription, drawings, and claims.

The aspects and embodiments of the invention disclosed herein relate toenergy converting apparatuses such as Stirling machines or engines andtheir constituent components and methods of operation. Without beinglimited to a particular theory or mechanism, in some embodiments theStirling engine and related system components use a working fluid(typically air, Helium, Nitrogen or Hydrogen gas) in a closed cylindercontaining a piston. As part of its operation, the expansion (heating)and contraction (cooling) of the gas drives the piston back and forth inthe cylinder. The work performed by this piston-motion is used to drivea generator (such as linear alternator) and produce electricity or tocreate pressure waves to drive a compression process. In one embodiment,a plurality of free pistons is used.

In way of further detail, the arrangement of moving masses used in oneembodiment of the energy converting apparatus includes an engine case orhousing, a mover, which includes a power generating piston, a displacer(which can include a mass used to displace the working fluid), and apassive balancer. All of these various elements are coupled togethereither directly or indirectly and vibrate and move to varying degrees. Aring frame that includes a support and ring portion through which theengine housing is suspended along its longitudinal axis, an axisparallel to the longitudinal axis or an axis equivalent thereto, isdescribed in more detail below.

In some embodiments, the Stirling machines and related technologies areconfigured to collect solar energy and convert it to electricity oruseful work as part of an energy converting apparatus. Since theStirling engines described herein use a closed system containing afluid, electrical subsystems, cooling subsystems, and other elementsthat are subjected to significant heating, different embodiments of theinvention relating to heat exchangers and over insolation control arebeneficial to the device operation. “Insolation” is a measure of solarradiation energy received on a given surface area in a given time.Accordingly, “over-insolation” is an excess of solar radiation energy(i.e., more solar radiation than the system can thermally process)received on a given surface area in a given time.

As discussed in more detail below, heat exchangers and over insolationcontrol methods are used to dissipate and otherwise direct the receivedsolar energy to prevent damage to the overall system. In addition, sincethe energy converting portion of the system includes one or morevibrating free pistons or Stirling engines and a moveable solar energyreceiver portion mounted in, an elevated position, controllingvibrations is another feature of the invention. The description thatfollows provides specific details relating to various energy convertingapparatus and components that address these problems and others. Beforeconsidering these details, exemplary systems embodiment suitable forconverting solar energy into electricity or mechanical work are shown inFIGS. 1A and 1B. Although solar energy, sunlight, thermal energy, andother terms are used throughout, they are not intended to limit theembodiments herein. In general, the invention relates to systems,subsystems, methods, devices, apparatuses, and components, whichcooperate to convert or transform one form of energy to another whileusing the various methods and apparatus described herein.

It will be appreciated that the apparatus described herein and its manycomponents can be sized and scaled according to the desired size of theenergy converting apparatus. Thus, while references may be made to thesize of the apparatus and/or its individual components, such referencesare for illustrative purposes only and the sizing or scaling of theapparatus and its components can be altered without departing in any wayfrom the scope and spirit of the invention.

Energy Converting Apparatus and System Overview

As shown in FIGS. 1A and 1B, an embodiment 10 for collecting andconverting solar energy is shown. Solar energy from the sun 12 (λ)impinges upon a collector 14 (alternatively a dish, array of panels,reflector, or concentrator). In one embodiment for use with solar energycollecting, the collector is a mirror or other reflective surfacedisposed on each panel. As shown, a plurality of substantially identicalconcentrator panels (reflecting elements) 16 encircle a common center toform a curved surface capable of directing light to the energyconverting apparatus 18 (ECA). Each panel has a plurality of edges. Agroove or slot 20 can be incorporated in some embodiments of theconcentrator to facilitate changing the angle of the concentratorrelative to a supporting post or pier 22. Energy collected is redirectedto the ECA 18 as shown. The concentrator 14 and energy convertingapparatus 18 are designed to slew with the sun by using the drive unit24. In one embodiment, a biaxial drive unit is used. A boom 26 connectsthe energy converting apparatus with the concentrator. The boom 26 isconfigured to accommodate the pier 22 as the concentrator 14 isarticulated about its rotational axis.

In other embodiments, the same shaped collector can be utilized toconcentrate other forms of energy, for example radio or microwavetransmissions. Such collectors or dishes are frequently used to collecttransmissions from geostationary or orbiting satellites. In such cases,the surface of the concentrator panels is made of a material whichreflects the energy waves of interest. In one embodiment, the surface ismade of a metallic mesh to reflect microwaves. In one embodiment, thediameter of the collector or dish ranges from about 4.7 m to about 6 m.In another embodiment, the collector or dish is between about 1 m andabout 50 m in diameter. As discussed in more detail below, in oneembodiment, the collector or concentrator includes a plurality ofcomponents that each have a flat or low profile such that the componentshave an optimized packing density and a size/shape profile that areamenable to conventional shipping on transport. Thus, as shown in FIGS.7, 9, 11, 14 and others, the components of the chassis and/or collectorcan be sent in one or more conventional boxes, such as a flat box, andrapidly assembled in the field to quickly install an energy convertingapparatus and collector system. The use of flat elements to build thechassis which receives the panels is one feature of the invention.

As shown, in FIGS. 1A and 1B, a biaxial drive unit (or drive) 24 isconfigured to move the concentrator 14 and the energy convertingapparatus 18, in accordance with one embodiment. The concentrator andthe energy converting apparatus can rotate through a full 360 degrees.In addition, for compass direction (azimuth), elevation can be adjustedup to about 162 degrees. In addition, the concentrator can be parallelto the ground while facing skyward or slant towards the ground during anon-operative or stow mode. Since the systems shown in FIGS. 1A and 1Bare typically used for electricity generation, an electronics package 34or an AC power output 28 are present in some embodiments.

As shown in FIG. 1B, a boom 26 is operatively coupled by a weld or otherfastener to a chassis 30, which includes a plurality of elongate radialprojections, elongate members, structural members, panel arms, or ribs32 a-n. These members are flat or narrow along one dimension tofacilitate flat packing and shipment. In some embodiments, the panelarms 32 are about 2 m long, about 0.25 m high, and about 0.035 m wide.The concentrator panels 16 are affixed to the panel arms 32. In oneembodiment, the concentrator panels 16 possess a substantially identicalgeometry. This offers advantages when assembling the concentrator todirect incident solar energy into the energy converting apparatus. Whenassembled, a star-shaped hole 19 is formed in one embodiment. As shownin FIG. 1B, the groove or slot 20 in the concentrator is sized relativeto the diameter of the pier or post 22 to allow for the concentrator 14to move through a wide range of motion. Thus, one embodiment of theinvention relates to a concentrator that includes a plurality ofsubstantially identical panels, such that when combined, the pluralityof panels form a three-dimensional surface with a slot that is sized toaccommodate clearance to the pier for given a range of motion of theconcentrator. In one embodiment, each panel has two pairs of edges, eachpair of edges radially oriented to a different pair of nonconcentriccircles.

The energy converting apparatus (alternatively referred to in oneembodiment as a heat drive or Stirling machine/engine) includes a freepiston Stirling engine and various cooling, sensing, heat exchanging,vibration balance, and other subsystems. The energy converting apparatusreceives the solar energy and produces useful work or electricity aswell as waste heat. The pier or post supports the collector, biaxialdrive, and energy converting apparatus. The pier and a portion of thedrive assembly that is collinear with one rotational axis of the biaxialdrive are also hollow in one embodiment to facilitate the routing ofwire or cables. In other embodiments, the energy converting apparatusinclude solar photovoltaic converters or radio and microwave detectors.The use of a biaxial drive also facilitates advantageous routing ofpower or fluid delivery cabling. Specifically, the use of an offsetdrive mechanism allows cabling to be centrally routed through the postor pier used to support the energy converting apparatus.

In FIG. 1C, the outer skin, housing or cover 50 of the energy convertingapparatus 18 is shown. As part of the operation of the device, the cover50 is designed to satisfy certain conditions. Specifically, the covermust not burn or melt and it also must hold up to snow, ice, rain andhail or any other foreseeable weather event. In order to achieve some ofthese objectives, in one embodiment the cover is made from a sheetmolding compound (SMC). Other suitable materials for the cover include,for example, steel, aluminum, plastic, and/or fiberglass.

Further, with respect to FIGS. 1C and 1D, the connection of the outercover 50 with the frame represents another design feature of the energyconverting apparatus. As shown, the two cover portions connect relativeto the top spar or slewplate 52 of the frame such that the top spar ofthe frame forms the central spine of the top of cover. This design ofthe frame allows the top spar of the frame to shield the internalStirling engine portion and receiver components of the energy convertingapparatus 18. If a plastic or other covering were used, instead of usinga portion of the frame as a heat shield, the plastic could melt or catchfire, thereby resulting in damage to the energy converting apparatus.This melting would occur during the process where the device articulateswith the sun. Thus, a beam of concentrated light moving along the spar52 is prevented from damaging engine components by the additionalshielding of the spar.

Thus, in part, one embodiment of the invention relates to using acomponent of the frame to provide heat shielding, such as by a slewplate on the top of the energy converting apparatus, with respect to theengine or receiver portion. Although the top portion of the frame isused as a radiation shield, another part of the frame could be used as ashield in other embodiments. Thus, a heat shield formed from a frameportion can be used on the top, side, or bottom or any portion of theenergy converting apparatus.

As shown in FIGS. 1D-E, the heat shield or slew plate 52 also can beused for the frame. Another approach is to use a separate plate on thetop of the engine housing in addition to a separate frame system.However, this is inefficient and adds weight to the apparatus. As shown,the slew plate 52 portion of the frame acts to protect the engine andother components from the intense beam of sunlight, which in someembodiments passes over (under or to the side) the engine housing whentracking on sun or off sun. This design embodiment combines the slewcone 58 having aperture 60, the faceplate 62, and the engine housingframe into one piece. The frame and slew cone 58 and faceplate 62 act asa combination heat protection system when the beam is moved in and outof the aperture 60.

Since managing heat within the various energy converting apparatusembodiments is important to viable device operation, it useful toconsider the embodiments shown in FIGS. 2A, 2B, and 2C. From these viewsof the energy converting apparatus 18, it is significant that theoverall apparatus is divided into a receiver portion 56 and a Stirlingengine portion 54. Referring to FIG. 2C, in one embodiment, the receiverportion 56 includes the faceplate 62, the slew cone 58, the receivercone 100, and associated components. Referring to FIG. 2B, in oneembodiment, the engine portion 54 includes the heater head 102, engine55, and engine housing 57, and associated components. In one embodiment,such as that shown in FIG. 2B, the energy converting apparatus 18includes a receiver assembly 56, onto which light impinges, and anengine portion 54. The engine housing 57 is also shown, and may includeseveral components that form an outer pressure boundary of the Stirlingengine 55. In one embodiment, the energy converter is a free pistonStirling engine having an alternator, which generates electricity as thefree piston oscillates. In one embodiment, optional fans help to reduceand/or vent excess heat in the energy converter 18.

As shown in FIG. 2C, in some embodiments solar radiation 12 from thecollector is initially incident on the face plate 62 or slew cone 58 asthe overall system clews to track the sun. During normal operation,solar radiation is directed to a focal point at or near the aperture 60,after which the beam of radiation expands through the receiver cone 100to impinge on a heater plate 102, which is discussed in more detailbelow. In one embodiment, such as that shown in FIG. 2F, one or moreover-insolation sensors 115 can be used to generate data or detecttemperature changes based on excessive solar energy incident upon theECA, and such that movement of the drive assembly can be triggered toprevent over-insolation.

In general, thermally decoupling the engine assembly and the receiverassembly is one aspect of the invention. In some embodiments, thermalisolation is achieved using a bellows seal or an accordion seal 150,such as that shown in FIGS. 3H-J. As will be appreciated, any sealconfiguration can be used which results in thermal isolation. In oneembodiment, a silica fabric can be used to form a bellows seal betweenthe receiver assembly and the engine assembly. However, the embodimentsof the invention are not limited to silica fabric, and any materialsuitable for shaping into a bellows seal can be used in variousembodiments subject to other system parameters.

A related aspect of the invention is isolating the vibrations of thereceiver from the vibrations of the Stirling engine. The use of abellows seal allows the seal to flex and resist tearing duringoperation. As a result, the bellows seal helps isolate the respectivevibrations from the receiver assembly and engine assembly. With that asbackground, specific details relating to the receiver assembly and itscomponents elements are discussed below.

As shown in FIGS. 3A and 3B, the outer portion of the receiver assemblyincludes a faceplate 62. The receiver face plate protects the rest ofthe components from solar energy spilling or otherwise impinging on themfrom imperfect mirrors, auto-commissioning, over-insolation control,failed sensors and other events. The faceplate 62 also protects theother components when the dish moves the beam of concentrated solarenergy into the aperture or out of the aperture.

In addition, the faceplate 62 absorbs and stores the energy before it isemitted by radiation, reflection, conduction, or convection to air orother materials. The receiver faceplate 62 is designed to be easilyreplaceable in the field in case it becomes damaged from concentratedsolar energy. In one embodiment, the faceplate 62 is made out of metalto be impact resistant. In contrast with a ceramic design which couldbreak due to hail or thermal cycling, the faceplate offers manyadvantages. The faceplate 62 can include a ceramic coating or othersuitable thermal treatment to reduce solar energy absorbance.

As shown in FIGS. 2D, 3A and 3C, a receiver slew cone 58 is used invarious embodiments. The slew cone 58 is used to protect the thinreceiver foil 110, 111, the receiver cone 100, and other components fromconcentrated solar energy. It also functions to absorb and store energyduring different phases of operating the concentrator and energyconverting apparatus. Sensors 114 are used to determine how much energyis spilling or impinging upon the slew cone (or other surfaces of theapparatus) (FIG. 3C). Thus, the relevant sensors 114 collect sensordata, such as temperature data. This sensor data can be used to increasethe amount of energy entering the receiver, and thus increase systemperformance. In one embodiment, the diameter of the slew cone rangesfrom about 24 mm to about 280 mm. Similarly, the diameter of theaperture ranges from about 80 mm to about 120 mm. In a preferredembodiment, the aperture is about 95 mm+/−0.5 mm.

Alternatively, this sensor data can be relayed to the drive unit tocause light from the concentrator to be distributed around the heaterplate 102 to reduce the likelihood of overheating the engine or othercomponents of the energy converting apparatus. The sensors 114 used tocollect sensor data can be selected from all sensors that can fit withinthe energy converting apparatus. As an example, suitable sensors caninclude, but are not limited to, temperature sensors, thermocouples,displacement sensors, accelerometers, radiation sensors, light sensors,or any other sensor.

The slew cone 58 of FIGS. 3C and 3D, and its other, embodiments, isdesigned to be easily replaceable in the field, in case a temperaturesensor fails and the slew cone becomes damaged. As shown in FIG. 3D, theangle 59 of the receiver slew cone also allows for more energy toreflect from the slew cone and into the receiver, though other anglesare possible. The slew cone angle 59 can range from about 0 to about 80degrees. In a preferred embodiment, the slew cone angle 59 is betweenabout 38 to about 41 degrees. In turn, this increases the performance ofthe energy converting apparatus. In one embodiment, a surface of one ormore of the receiver assembly components (e.g., the faceplate, slewcone, receiver cone) is coated with a thermal barrier coating (TBC) orthermal spray (e.g., plasma, flame, cold, electric arc, or HVOF spray).TBC is a metal, ceramic, or cement coating that helps reduce thetemperature of a component by reflecting energy from it, and by means ofa temperature drop due to conduction across the coating. In oneembodiment, a TBC coating is used. However, in other embodiments a TBCcoating is not used.

The receiver assembly can also include one or more sensors 114 invarious embodiments to collect data that in turn can be used to enhancedevice operation or to safeguard the energy converting apparatus or itscomponent elements. In one embodiment, temperature sensors areincorporated in the receiver assembly. In one embodiment, such as thatshown in FIG. 3C, these sensors are located on the backside (notincident with solar energy) of the faceplate 62 and slew cone 58 toprotect them from concentrated solar energy and some environmentalelements.

In general, to date, receivers have only been of certain types, such asdirect illumination receivers (DIR), reflux, or heat pipe receivers. Asdepicted in the figures, the receiver assembly embodiments describedherein do not use a bank of tubes to transfer energy to the engine likeDIR's, and are dissimilar to the other receiver designs mentioned above.The material selection and properties of the receiver assemblyembodiments and their constituent parts offer many advantages, one ofwhich is that they are more economical than other designs. The novelreceiver design is also complimentary with the Stirling engine's lineararrangement of masses and geometric details.

In one embodiment, as shown in FIG. 3E, the receiver cone 100 is made ofmetal. Further, the receiver cone lip 101, which is positioned near theaperture 60, aides in preventing the receiver foil 110 from beingdamaged by incoming solar flux. In one embodiment, the receiver cone 100is designed to oxidize when concentrated solar energy enters thereceiver to improve the receiver performance with a dark surface. Thereceiver cone 100 is made out of metal to be impact resistant and lesscostly to manufacture. In one embodiment, the outer receiver conediameter ranges from about 260 mm to about 280 mm. In one embodiment,the inner receiver cone diameter ranges from about 95 mm to about 105mm.

As shown, in FIGS. 2C, 2D, and 2E, there is a single piece of insulation106 encapsulated between the receiver cone 100 and the receiver foil110, 111 in one embodiment. Multiple insulation portions can be used inother embodiments. Typically, the insulation 106 is a porous material,such as a silica material. In some embodiments, more than one unitarypiece of insulation can be used. In one embodiment, the receiver foil110 is welded to the thicker receiver cone 100 to encapsulate theinsulation 106 to form a receiver pack 100′. In one embodiment, thereare two receiver foils 110 and III. Receiver foil 110 is welded to lip101 and to receiver foil 111, and receiver foil 111 is welded to lip103.

Further, the receiver pack 100′ forms a curve 113 configured to receivea complementary curve 115 formed in the engine insulation 108, therebyforming a seal which prevents hot, buoyant air from escaping thereceiver through natural convection. Welding the receiver foil 110 tothe lip 101, on the side of the receiver cone 100 which opposes theincident light, helps improve the receiver reliability. This followsbecause the foil is welded to the receiver cone on the side opposite ofincoming sunlight 12 since the thicker receiver cone can handle thegreater solar flux (FIG. 2E, showing a partial blowup of FIG. 2D).

As shown in FIG. 3E, there are several receiver support brackets 152.The receiver support brackets allow the receiver assembly to bedecoupled from the engine since the receiver assembly is attached to thespars, which constitute part of the frame. Receivers from othercompanies have failed at times due to the receiver vibrating too muchwhile attached to the engine. PEM® nuts are added to the receiverbrackets to allow for more rapid assembly and servicing.

With respect to FIG. 3F, an energy balance for the receiver can bewritten by either of the two equations:Q9=Q1+Q2+Q4°Q8Q7=Q4−Q3−Q5−Q6

-   -   Q1: Reflected power from the concentrator incident on the        faceplate    -   Q2: Reflected power from the concentrator incident on the slew        cone    -   Q3: Radiation emitted and reflected from the receiver out of the        receiver    -   Q4: Total power intercepted by the receiver from the        concentrator    -   Q5: Total power from convection leaving the receiver    -   Q6: Conduction through the receiver insulation before convection        and radiation off of the receiver foil    -   Q7: Useful power entering the engine    -   Q8: Total power reflected from the concentrator which does not        impinge upon the slew cone or faceplate, or enters the receiver    -   Q9: Total power reflected from the concentrator

As shown in FIGS. 3H and J, the engine insulation 108 uses a metal foil109 that encapsulates the engine insulation 108 and the insulation seal150. In one embodiment, the seal 150 is attached to the foil 109 withhigh temperature silicone. Clamp 112 clamps over the metal foil 109,which covers the outer surface of the seal 150 and the engine insulation108. The insulation 108 is beneficial because it helps reduce thermallosses from the engine, allowing the engine to operate more efficiently.The metal foil 109 helps to give the insulation seal 150 rigid support,in addition to reducing convection should the insulation seal 150 beginto fail. As shown in FIG. 3G, a groove or curve 115 in the engineinsulation 108 that helps reduce convection and thermal losses in thereceiver is also illustrated. In addition, a groove 164 along theengine-facing surface enables temperature sensors or other sensors to beattached to the engine to monitor temperature to help reduce convectionand thermal loses in the receiver.

An exemplary bellow insulation seal 150 for decoupling, both thermallyand vibrationally, the receiver assembly from the engine assembly isshown in FIG. 3J. The insulation seal 150 allows the receiver to bedecoupled from the engine while scaling the receiver from convection. Itis attached on the engine insulation 108 and receiver insulation packs100′. It is formed from flexible material to accommodate and reducetransmission of vibration from the engine and engine housing.

Collector or Dish Assembly, Stow Position, Panel Geometry and OpticalFeatures

Referring to FIG. 4, the structural unit 10 generally includes amechanical/structural portion 204 and a receiver or generator portion,such as a Stirling engine/generation portion 18. Themechanical/structural portion 204 includes a collector portion 208including segments or panels 16 supported by panel arms 32 (elongatemember or ribs). In one embodiment, the segments or concentrator have areflective coating (such as tiles) or are mirrored, and the panels 16collectively form a solar collector 208, which concentrates and focuseslight toward the Stirling engine/generation portion 18. A boom assembly26 includes two boom arms 228, 228′, an engine platform 232, and achassis anchor 260. The chassis anchor 260 is mounted on a driveassembly 24, which is in turn mounted on a pier 22 which anchors thesystem 204 to the earth. The pier 22 also supports the system'selectronics package 34. In one embodiment, the pier is about 3 m long,and about 0.2 m in diameter.

Two segments 252 and 252′ do not touch one another and so form anopening or slot 20, which permits the solar collector 208 to move aroundpier 22. In addition, in one embodiment, the two boom arms 228, 228′ arespaced apart sufficiently to allow the solar collector 208 to pointdownward when in the stowed position. The collector 208 points about 160degrees from vertical when in the stowed position.

Referring to FIGS. 5A and 5B, in the stowed position the Stirlingengine/generation portion 18 is brought near the ground and the two boomarms 228, 228′ pass around the pier 22. This permits the collector 208not to collect dust and debris or be damaged either when not in use orwhen faced with the possibility of excessive wind load. In oneembodiment, a lock (discussed below) near the base of the pier 22,engages the engine platform 232 and holds the assembly stably inexcessive wind conditions.

In more detail and referring to FIG. 7H, the panel arms 32 are attachedto a hub 256, which is in turn attached to the chassis anchor 260. Inone embodiment, the hub 256 includes two substantially planar matingsurfaces that define a plurality of holes sized to receive pins locatedon the elongate members 32. The boom arms 228, 228′ are also attached tothe chassis anchor 260. Additional struts 274, 274′ are spaced about thepier 22 and attached to the chassis anchor 260. The struts 274, 274′help support the boom arms 228, 228′. In one embodiment, the chassis isthe collection of elements to which the panels attach and receivestructural support.

Referring also to FIGS. 7A-1, the engine platform 232 (FIGS. 7B and 7I)is attached to the boom arms 228, 228′ by U-brackets 300 (FIG. 7C). Theengine platform 232 (FIG. 7B) is offset from the centerline of thecollector portion 208 so that when the Stirling engine/generationportion 18 is positioned on the engine platform 232, the focal axis ofthe collector portion 208 is coincident with the longitudinal axis ofthe Stirling engine/generation portion 18. The set of panel arms 32(FIG. 7F) are attached to the hub 256 to form the convex shape of thecollector chassis 208. The chassis anchor 260 is attached to the hub 256concentric with the hub's 256 center. The hub 256 (FIG. 7J) isconstructed from two circular plates 258, 258′. The plates 258, 258′include a cut-out 259 into which the chassis anchor 260 is mounted. Theplates 258, 258′ are separated from each other by the panel arms 32(FIG. 7N).

Referring to FIG. 7N, attaching the panel arms 32 to the hub 256 areshoulder bolts 270, which control the lay of the hub plates 258, 258′ toa high level of precision. Although reference is made to various boltsthroughout, for all of the embodiments described herein, any suitablefastener element can be used. Suitable fasteners include, but are notlimited to bolts, screws, rivets, welds, adhesives, and othermechanical, electrical or chemical elements suitable for connecting,attaching, coupling, linking or fusing two objects. The assembly of thehub 256 with the panel arms 32 provides an alignment base to which thepanel arms 32 can be quickly and easily attached without requiringadditional alignment when the panel segments 16 are attached.

Such a configuration makes it possible to assemble an array of thesesystems without additional alignments being required. Each hub is amating surface. The hub is substantially circular with a diameter ofabout 1 m and a thickness of about 4 mm. A pair of these hub plates 258(FIG. 9B) sandwich the panel arms between themselves. This results inparallel mating surfaces with radially oriented elongate members. Thisarrangement of hub plates and elongate members or ribs includes achassis upon which panels may be disposed, aligned and supported.

With respect to the elongate members (or ribs) described herein, theplurality of structural elongate members radiate out between to commonmating surfaces (hub plates). As a result, any surface waviness or otherdefect on the two common mating surfaces is thereby cancelled outbecause none of the structural members share parallel paths. Inaddition, in embodiments relating to the chassis that supports theconcentrator panels, upper and lower mating surfaces are forced to beperpendicular to the central axis of the assembly by pinning eachstructural elongate member (or rib), which radiates outward from bothmating planes.

In part, as described herein, one embodiment relates to a method ofassembly that through the arrangement and means of attachment ofcomponents, coupled with consistent part geometry (minimal part to partvariation), results in a quickly constructible chassis and concentratorwith negligible deviation from nominal (ideal) on mating surfaces forthe solar concentrator. Previous concentrators have relied upon a threepoint attachment for each panel of the concentrator so as to allow for“tuning” by trained technicians to dial in concentrator optical pointingaccuracy. The described embodiment chassis requires no such “tuning”,and therefore can be assembled by untrained individuals with a basicconstruction skill set. With respect to the concentrator and supportingchassis of ribs and hub plates, no tuning is needed. As used in thiscontext, no tuning is defined as an assembly methodology which requiresno special measurement equipment or adjustment of assembly. Theconcentrator and chassis can be quickly assembled based on an orderedsequence of steps followed by torquing fasteners a defined amount. Thisdefined amount typically ranges from about 20 Nm to about 250 Nm.

In one embodiment, panel tilt is controlled by the panel arms(concentrator structure supporting panels) being pinned with shoulderbolts through both upped and lower flange attachment locations to acentral hub. The use of shoulder bolts improves optical performance ofthe concentrator. In general, the benefit of the shoulder bolts is thatthey cause precise angular alignment of the reflective panels with thereceiver. The shoulder bolts precisely align the panel arms to the hub,thus aligning the reflective panels which are mounted to the panel arms.

The shoulder bolts control the tilt of the panel arms with thetangential alignment tool controlling sweep so the fastening holes onthe panel arm align with the attachment points on the panels. Thecombination of the panel arm hub plate and tangential alignment toolforms a triangle, thereby controlling the angle that the panel armsradiate out from the hub. The alignment tool is used at a time in whichthe panel arms are secured to the hub and is removed after the shoulderbolts (securing fasteners) are tightened.

To ensure alignment of the ribs or panel arms relative to the hub andeach other, an alignment tool is used in assembling the ribs to the hubplate. A tangential alignment tool such as that shown in FIG. 8 isutilized where panel arms are installed and fully torqued with the hubbefore panels are installed. The amount of torque applied to attach andautomatically align each panel is about 91 Nm. The hub plate has aseries of first alignment points located, in one embodiment, around theperiphery of the hub plate. In one embodiment, these first alignmentpoints are studs. Each of the ribs has a hub end for attachment to thehub and a distal end, which has a second alignment point. In oneembodiment, the second alignment point is also a stud.

The alignment tool 400 (FIG. 8) is an elongate body 404 having a firstend 408 and a second end 408′. A first attachment unit 412 is located atthe first end 408 of the elongate body portion 404 and a secondattachment unit 412′ is located at the second end 408′ of the elongatebody portion 404. In use, the first attachment unit 412 is for attachingthe alignment tool 400 to a first alignment point on the distal-mostpoint (with respect to the hub) on the panel arm, and the secondattachment unit 412′ for attaching the alignment tool 400 to a secondalignment point on the hub plate to thereby align each panel arm withrespect to the hub plate prior to fixation of the panel arm to the hubplate.

Upon tightening of the assembly a predetermined amount, the alignment,which is within a predetermined specification, is achieved. The chassisanchor 260 (FIG. 7L) is constructed of two anchor arms 450. Referring toFIG. 9C, one end of each anchor arm 450 includes a circular engagementportion 454. The circular engagement portion 454 bolts to the driveassembly 24. The other end 458 of each arm 450 fits within the notch 259of the hub 256 and is bolted to the hub 256. Referring to FIG. 9E, twohub closure plates 255 are secured between each of the anchor arms 450,as shown in FIG. 7H.

Referring to FIGS. 7J and 9A-F, in some embodiments, the chassisassembly includes a plurality of panel arms 32, two hub plates 258,258′, two anchor arms 450, two hub braces 257, two hub closure plates255, and four hub side braces 261.

Referring to FIGS. 6 and 7K, the pier 22 is anchored to a concrete base500 by a plurality of bolts 504, which protrude through a pier baseflange 508. The electronics package 34 is bolted to the pier 22 usingU-bolts 246. The pier has a drive flange 512 on the opposite end, ontowhich the drive assembly 24 is attached. In one embodiment, near thepier base flange 508 is positioned a self centering pier lock 514. Thepier lock 514 engages with a saddle portion of the engine platform 232when the device is in the stowed position.

The chassis anchor 260 is attached to the pier 22 by way of the driveassembly 24. The drive assembly 24 provides two degrees of rotationalfreedom to the collector portion 208. The drive assembly 24 permits thecollector portion 208 to rotate about the vertical (azimuth or z-axis)of the pier 22. The drive assembly 24 also allows the collector portion14 to rotate about one of the horizontal axes (elevation or y-axis) andthereby change the vertical direction in which the boom arms 228, 228′point. Referring also to FIG. 10, the drive assembly 24 attaches to asecond pier flange 512 by way of a plurality of bolts 550, which engagea drive flange 554. The anchor arms 450 engage both sides of thevertical drive 558. In this way, when the collector 208 is pointedstraight up, the anchor arms 450 are located parallel to and adjacent tothe pier 22.

The drive assembly includes two axes of rotation. These axes are offsetand are such that the rotational axis for rotation in the verticaldirection and the rotational axis for rotation about the pier 22 do notintersect. The rotational axis about the pier 22 is coincident with theaxis of the pier 22 itself. The vertical rotation axis is off-set fromthe axis of the pier 22, such that when the concentrator is pointedstraight up, the axis of symmetry from the concentrator 208 isco-parallel with the axis of the pier 22, but not coincident (FIG. 6).This arrangement allows the wiring from the generator to pass into thepier without tangling with the drive units. In addition, since each ofthe two axes associated with the biaxial drive unit are offset, eachdrive unit has its own origin and coordinate system. In light of theknown offset values and relative spacing between the origins (0, 0, 0)and (a, b, c), it is possible to transform between each of the twospatial coordinate systems.

The drive assembly, drive unit, or biaxial drive unit is a compact selfcontained unit, which provides all the required degrees of freedom fortracking the sun with the solar concentrator. These degrees of freedominclude an axis which is normal to level ground for compass direction(azimuth axis), and another which is orthogonal to the first forestablishing elevation of the dish (elevation axis).

The elevation axis is set behind the azimuth axis so as to expose thetop of the azimuth axis and a hole or slot defined in the drive housing.When coupled with a hollow shaft or pier for the azimuth axis, thisallows for system wire or cable routing directly down through the centerof the drive. This addresses the need for a separate wire managementscheme.

With respect to the drive unit, an elevation axis, which is set behindthe azimuth axis when the dish is pointed up in the zenith position,allows for the use of a hub, which is offset from the post and thus hasbuilt in clearance between these two structural components. The benefitof this arrangement is a smaller structural cross section for the hub.

Referring to FIG. 11A, in one embodiment, the panels 16 that make up thecollector 208 are non-radial segments. That is, inner portion 600 ofpanel 16 has a different angular width than outer portion 604 of thesame segment 16. As shown in FIG. 12A, the segment shape permits sixidentical segments 16 to be used to form or comprise the collector 208while permitting the opening or slot 20 to be formed with two parallel,non-radial edges. A further embodiment of a concentrator panel havingnon-radial segments is shown in FIG. 13. In one embodiment, the panelsare about 2 m long, about 2.2 m wide, and about 50 mm thick. In onepreferred, but non-limiting embodiment, each panel segment is made up ofa structural substrate (sheet molded compound or stamped steel) withattachment bosses and a reflective surface (thin glass mirror tilesdeformed into a 3 dimensional surface or reflective film), which isbonded in place with a pressure adhesive.

Referring back to FIG. 12A, the inner portions 600 formtriangular-shaped openings 608 between adjacent panels near the center619 of the collector 208, except between panels 252 and 252′, which areadjacent to the groove 20. This configuration maximizes the reflectivearea by not allowing the opening 20 to taper outward toward the outercircumference. This shape makes the manufacturing and assembly of thecollector easier, since only one segment shape need be manufactured,stored and used. The panel arms, hub plates (or substantially planarmating surfaces), and other elements having a flat or partially flatprofile can be stored and shipped with greater ease to remote locationsfor in field assembly.

In one embodiment, each segment 16 includes a solid polymeric glassresin having a ribbed curved backing, which includes bolting bosses 654that correspond the bolt locations on the panel arms 32. The glass resinis used because of its strength, non-shrinkage, UV and heat resistantproperties. These bolting bosses 654 permit the segments 16 to be boltedto the panel arms 32 using spherical washers to reduce deformation ofthe surface as a result of bolting the surface to the panel arms 32. Thesegment 16 itself is non-planar, but is curved so as to form, whenassembled with other segments 16, a focal point at the correct distancefrom the collector 208. In one embodiment, the top surface of each panelhas a reflective surface. For example, the reflective surface can beformed using a plurality of reflective tiles. In one embodiment, thefront surface of each of the plurality of panels is made reflective byattaching a plurality of about 1 mm thick silvered glass tiles usingadhesive. The reflective or mirrored surface of the collector 208 can beformed using various suitable reflective or partially reflectivematerials.

Upon assembly, the mirror segments or panels 16 are installed in amanner to form a precision shell that is utilized as a fixture to locatethe radial position of the panel arms 32 with respect to the chassisanchor 260. Each mirror segment or panel 16 has two linear sets of threebolting supports 654, as shown in FIG. 11A-B and FIG. 14. Each linearset of connection points is attached to one panel arm 32. There is aninterface at each location where a bolting support 654 of a panel 16meets a corresponding bolt location on a panel arm 32.

In one embodiment, the concentrator is comprised of six identical panelsegments. The geometry of each panel is such that when assembled ontothe chassis, a slot is left in the dish through which the supportingpost translates and that dish is articulated from tracking the sun tostowing the dish. In one embodiment, individual panel geometry balancesthe ability to use a common identical panel segment for all sixlocations on the dish while at the same time maximizing reflectivesurface area. This results in open star pattern at the center of thedish as discussed above and shown in various figures.

As shown in FIG. 12B, in one embodiment, the assembly procedure startswith the first panel 252′ to the left of the opening 20 between segments252 and 252′ when facing the mirrors. The panels 16 are attached to thepanel arms 32 starting with the first panel and the first and secondpanel arms, and continuing in a clockwise direction. In particular, thefirst panel is installed onto the first 32 a and second panel 32 b armsusing a fastener. In one embodiment, the fastener is a bolt 700 (FIG.15A) and nut 704 (FIG. 15B), although any suitable fastener can be used.In one embodiment, at each interface, the panel arm 32 includes a bolt700 that extends both above and below the panel arm 32 as shown in FIG.16.

Referring to FIG. 16, attachment of a panel to a panel arm 32 at anattachment boss 654 of the panel is shown, in accordance with anembodiment of the invention. The panel is bolted to the panel arm usinga bolt 700 which passes through a hole in the panel arm pad (i.e., theportion of the panel arm to which the panel attaches) and threads intothe attachment boss 654. Below the panel arm pad, the bolt 700 secures aconvex/concave washer pair 714. Above the panel arm pad, the bolt 700secures a convex washer 706 and a panel concave boss 710.

In another embodiment, on the bolt 700 above the panel arm 32, the panel16 is secured to the bolt location (e.g., a panel arm pad) on the panelarm 32 with a flanged hex bolt head 700, a concave spherical washer 706(FIG. 15C) and a convex spherical washer (or convex insert) 708 (FIG.15D), with the concave surface facing up. In some embodiments, aconvex/concave spherical washer set is used. On the bolt above the panelarm 32, the panel arm is secured using a concave spherical washer 706,with the concave surface facing up. A nut 704 secures the washers 706,708 on the bolt 700. In general, the use of convex and concave matingsurfaces substantially prevents or reduces localized panel distortion.The amount of torque applied to attach each panel is about 25 Nm.

In use, the drive assembly 24 keeps the collector 208 pointed at the sunwhile the boom arms 228, 228′ keep the Stirling engine/generationportion 18 positioned properly from the collector 208.

Over Insolation Control

Embodiments of the invention also provide for the prevention and controlof over-insolation, i.e., an excess of solar radiation energy receivedon a given surface area in a given time. According to one embodiment,the energy converting apparatus' dish or collector is sized so that thesystem can produce about 3 kW_(e) when the solar insolation is about 850W/m². In one embodiment, the system is not sized to produce more thanabout 3 kW_(e) when the insolation is greater than about 850 W/m²; thus,solar energy must be rejected or the system will overheat and/orover-stroke. In general, the embodiments described herein relating tocontrolling over-insolation can be used with any system or device thatincludes a heat exchanger. In general, a heat exchanger refers to adevice that receives incident energy and actively or passively transfersit for energy generation. As a result, in various embodiments, theredirection of concentrated beams of energy can be used with variousenergy converting apparatuses including chemical energy conversion,thermal energy storage, gas turbine, multi-cylinder or multi-pistonengines, steam turbine, steam power towers, fuel cell, water-basedenergy generation systems and other systems.

Conventional approaches attempting to prevent over-insolation involvemechanical shading of a portion of the dish, mechanically blocking aportion of the focused light before it enters the cavity receiver, andventing heat from the cavity receiver via fans and ventilation pathways.

Embodiments of the invention solve the over-insolation problem with anapproach that purposefully misaligns the dish with the sun in acontrolled fashion so that a portion of the concentrated beam ‘spills’out of the absorber surface by, for example, spilling or redirecting outof the receiver aperture. The misalignment of the dish forces a portionof the beam to intersect with the slew-cone instead of entering thecavity receiver. As the energy content of the spilled or redirectedlight is potentially sufficient to damage the slew-cone and othercomponents (e.g., the face plate), the spilled or redirected light isrotated around the circumference of the aperture opening so that theslew-cone is able to cool down before the spilled or redirected lightmakes another pass.

In some embodiment relating to over-insolation control for ECAs, insteadof the incident beam of concentrated thermal energy being transmittedthrough an aperture, it contacts a heat exchanger or other surface ofinterest at a point or region. Under these circumstances, rather thanredirecting concentrated relative to an aperture, the energy isinitially directed along or through a substantially linearelectromagnetic radiation path. In turn, this path can be moved tochange the hot spot or point (or region) of concentrated thermal energyon a heat exchanging surface of an ECA.

According to one embodiment, the rotational speed of the solar energybeam is between about 0 to about 180 revolutions per minute (rpm). Morepreferably, the rational speed is between about 1 to about 30 rpm. Inone embodiment, a minimum rotational speed of about 11 rpm prevents theslew-cone from being damaged. However, it will be appreciated that avariety of rotational speeds may be suitable, depending on theparticular configuration of the system and the ambient conditions. Thedegree of spillage (or misalignment) determines how much heat isrejected by this method.

Should circular-tracking (or any other tracking pattern) or otherover-insolation controls (e.g., fans, partial spillage, etc.) beinsufficient to adequately lower temperatures, the dish may be elevatedsuch that the focused sun spot is above the heat drive untiltemperatures are acceptable to resume operation.

Referring to FIG. 17A, as light from the sun is incident upon orimpinges on the collector 208, the collector 208 focuses the sun towardthe Stirling engine/generation portion assembly 18. The Stirlingengine/generation portion 18 is positioned such that the focal point 800of the collector 208 is not at the heater plate 102 of the engine, butis forward of the heater plate 102. This allows the beams of light todiverge again before interacting with the heater plate 102. This is doneto prevent the heater plate 102 from experiencing the intense sunlightconcentrated at the focal point 800 of the collector 208. By having thebeam expand before impinging upon the heater plate 102, a larger area ofthe heater plate 102 can absorb the heat without melting, as shown inFIGS. 17B-17C. In some embodiments, the beam spills outside the edges ofthe heater plate. In some embodiments, the light or electromagneticradiation follows a substantially linear path or a non-linear (i.e.,converging on a focal point, then diverging) path.

Solar radiation is reflected off of the mirrored dish. The solarradiation forms two cones, as shown. In one embodiment, every conicsection that is normal to the cone's axis is called a heat-flux profile.The heat flux profile that impinges on the heater head of the engine isa function of dish distance. The heat flux profile is not uniform. Theheat flux towards the outer diameter of the profile is larger than Thattowards the middle. The arrangement described above was chosen so thatan insulative receiver could be used. The collector reflects more energythan is necessary to heat the plate under optimal sun conditions. Inthis way, when the conditions of sunlight are less than optimal, forexample during sunrise and sunset, the collector still focuses enoughenergy on the heater plate to cause the system to produce useable poweror initiate an engine cycle. The end result is that when the sun lightapproaches an upper limit or threshold as a result of the sizing of theconcentrator, there is too much energy focused on the heater plate 102,and the engine can overheat.

If the Stirling engine/generation portion 18 experiences too high of atemperature, the drive assembly 24 moves the collector 208 to reduce theamount of or prevent solar energy from entering the aperture. In thisway, the concentrated sunlight then transfers less power to the heaterplate 102, and the heater plate 102 temperature is reduced. Because thiscauses the faceplate 62 and slew cone 58 to become heated by the portionof the solar light that does not impinge on the heater plate 102, thedrive assembly 24 may not let the concentrated sunlight image remain onan area of faceplate 62 or slew cone too long. Instead, the driveassembly 24 oscillates so that the concentrated sunlight imageoscillates on and off the faceplate 62 and slew cone 58 to allow timefor them to cool. In one embodiment, shown in FIG. 17C, the driveassembly 24 moves so that the concentrated sunlight image 13 traces acircle around the periphery of the heater plate 102 and the slew cone.As will be appreciated, a circular track is only exemplary, and thesystem can track any pattern or can be randomized.

Referring back to FIG. 3F, during over-insolation conditions, the powerQ4 into the receiver 60 is decreased while the power incident on thefaceplate 62 (Q1) and slew cone 58 (Q2) are increased. Duringover-insolation conditions, some of the power Q1 and Q2 is absorbed withradiation and convection dissipating the absorbed power. This processallows the concentrator to be sized larger, which improves the yearlyenergy production, and the excess power is dissipated by, for example,the faceplate 62, slew cone 58, or any material outside the engine. Theconcentrated light can also be aimed entirely off the energy convertingapparatus so that the beam diffuses into the air.

During periods of higher solar intensities, fans can be used cool thereceiver. Although this is one approach, in a preferred embodiment,spilling or redirecting the excess solar energy onto the slew cone andfaceplate is preferred. However, excess solar energy can be spilled orredirected onto any material or component outside the engine. Thus, thefront parts of the receiver assembly absorb and store the excess thermalenergy before dissipating it from conduction, convection, and radiation.The faceplate and slew cone increase in temperature and dissipate morepower to the environment through conduction, convection, and radiation.During over-insolation control, the concentrator drive unit moves theconcentrator so that the concentrated light moves in a circular patternto spill or redirect on the slew cone and faceplate. However, othermovement patterns are possible, such as, for example, back-and-forth,triangular, square, or randomized.

In some embodiments, during over-insolation control, some concentratedlight still reaches the heat exchanger. In another embodiment, the driveunit is set to automatically engage when the engine is at maximum powerand the heater head temperature rises above a temperature set point toredirect or spill or redirect excess solar radiation on the face plateand slew conc. These features also allow less expensive metal faceplates to be used, since focused heating in one region of the face plateis avoided by the movement pattern. Thermal spray (cold, flame, plasma,electric arc, HVOF, etc.) which is a ceramic, metal or cement coating,can also be used on the face plate, slew cone, or other materials toreflect more energy and thus reduce the amount of thermal energyabsorbed.

In certain embodiments, the invention enables the use of an oversizedsolar concentrator. An oversized solar concentrator (e.g., a dish ormirror) is capable of collecting and/or concentrating more solarradiation than the system is capable of thermally processing withoutoverheating or damaging the system. If a larger solar concentrator isselected, such a device allows for greater energy production over thecourse of the year. This follows because more energy is realized duringnon-peak solar conditions. Non-peak solar conditions can beseasonally-related, such as when the daylight hours are shorter and/orsolar radiation is less intense, or weather-related such as duringcloudy weather. However, during peak solar conditions, an oversizedsolar collector can collect and/or concentrate more solar radiation thanthe system components can thermally process. As described in more detailbelow, the invention provides methods for reducing over-insolation,which can occur with an over-sized dish. As a general principle, theover-insolation or insolation control and regulation techniquesdescribed herein are not limited to Stirling cycle energy convertingapparatus, but can also be used with existing reflector based arraysused to heat water or generate steam. For example, many of the issuesrelating to hot spot movement can also be used with other non-Stirlingenergy converting systems that use solar energy.

Therefore, in certain embodiments the invention provides methods forreducing over-insolation. In some embodiments, this is accomplished byreducing the amount of solar radiation that passes through the apertureof the slew cone. For example, during peak solar conditions, excesssolar radiation can be spilled or redirected onto, for example, the slewcone or face plate rather than on the heat exchanger. Reducingover-insolation allows the system to continue producing power on hotdays when the coolant, heat exchanger, or engine would otherwiseoverheat. In one embodiment, when the direct normal insolation (DNI)(which is the direct intensity of sunlight) becomes too high,over-insolation control is engaged.

In some embodiments, reducing over-insolation enables the engine toperform better during normal operation by spreading out temperature fluxon the engine or other thermal components. Hot spots can form as aresult of imperfections in the solar concentrator and can contribute toreduced performance and reliability. Implementing over-insolationmethods during normal operation can spread any hot spots around andpotentially improve performance and reliability, and can extend theuse-life of the system. The lifespan and reliability of an engine andother thermal components can be reduced if they are heated too rapidlyover repeated cycles. Moreover, the impact of thermal transients can bereduced by slowing the rate at which the engine and other components areheated. For example, sensor feedback might indicate that the engine isheating too rapidly, and the over-insolation methods taught herein canbe used to reduce the amount of solar radiation impinging on the heatexchanger or other energy converting apparatus components.

Moreover, over-insolation control can be used during commissioning—thefirst days and weeks of installing or initializing the system—or afterreplacing components to prevent hot spots from being oxidized, whichcould lead to premature damage or reduced reliability and/or lifespan.Hot spots caused from an imperfect solar concentrator can also cause theheat exchanger to absorb more solar energy in the hot spots, which wouldcause the hot spots to become even hotter and could lead to prematurefailure. Thus, the methods for controlling over-insolation taught hereincan move the hot spots around during the first day/weeks of bringing thesystem or replacement parts on-sun to minimize formation of hotspots anddamage caused by imperfections in the solar concentrator.

In addition, the over-insolation control can reduce hot spot impact on amaterial sensitive to high peak fluxes or hot spots. For example, a heatpipe sodium vapor chamber or thermal energy storage module can haveburnouts and certain materials, and system components can be damaged ifpeak flux is too great. Moving the hot spots around would help preventhigh peak fluxes from damaging these parts sensitive to high peakfluxes.

In certain embodiments, over-insolation methods can reduce the thermalload on the coolant system, which would allow for better systemperformance. For example, over-insolation methods can be used to keepthe coolant maintained below an acceptable temperature if the coolingsystem cannot tolerate the high ambient conditions on a given day or ifcooling system performance degrades over time. In preferred embodiments,the coolant is maintained below a given temperature (e.g., about 80°C.). If the coolant overheats, the system can go into over-insolation toensure the coolant temperature stays cool enough. If over-insolation isnot engaged, the system would have to be brought off-sun, and would thuslead to a costly reduction in performance and energy realization.

Over-insolation methods can also be used so that the engine does notoverheat during thermal (or solar) transients when the head temperatureclimbs past its temperature set point (e.g., a normal operatingtemperature of the engine). The heater head control is configured tomaintain the head temperature at a specific temperature, but during athermal or solar peak it is possible that the heater head control and/orsystem will overshoot the temperature set point. If this occurs,over-insolation control can be used to reduce thermal input andtherefore reduce the chance of a significant temperature overshoot,which will reduce the lifespan and/or reliability of the engine.Generally, temperature overshoot is a rise in temperature of the enginewell beyond the temperature at which it is intended to operate. In oneembodiment, the preferred operating temperature of the ECA is about 600degrees Celcius. When a temperature sensor detects temperatures is about15 degrees above the preferred operating temperature, the drive assemblyis automatically engaged to spill excess solar radiation to lower theoperating temperature closer to the preferred operating temperature.

In certain embodiments, one or more components (e.g., the heatexchanger) are modified to absorb more solar radiation. Absorbance canbe increased, for example, by using thermal spray or by texturingcomponent surfaces. Oxidizing also thermally stabilizes components suchas the slew cone, receiver cone, or heater plate and is yet anotherapproach to safeguarding the ECA from overinsolation.

In another embodiment relating to insolation control, cloud covercontrol is used to protect the receiver and engine from solar thermaltransients. When the engine turns off due to clouds midday, it issusceptible to overheating or excessive thermal cycling when the cloudspart. This occurs from the time it takes to sense a temperature rise inthe engine temperature sensors. To overcome this, when the engine turnsoff and the concentrator continues tracking the sun, the concentratorbeam can be moved in the direction of a sensor on the slew cone. Whenthe sun comes out from behind a cloud, a temperature sensor, such as athermocouple, senses that the solar intensity has increased and theconcentrator is moved back to being centered in the aperture and theengine ‘bumps.’ Bumping the engine entails passing the working fluid inthe engine back and forth, which enables the engine to turn on beforethe receiver or engine overheats. Moving the piston in this way, inresponse to sun sensor detection of insolation, helps circulate theworking fluid in the engine (Helium, in one embodiment). This serves todistribute heat, which diminishes hot spots that can thermally fatiguethe engine and limit its life.

As described above, various over-insolation control methods and devicesmay be implemented that uses sensors to trigger a change in the amountof solar energy that reaches a heat exchanger or other surface suitablefor transporting thermal energy for use in a Stirling cycle. Theseover-insolation control methods may be embodied in may different forms,including, but in no way limited to, computer program logic for use witha processor (e.g., a microprocessor, microcontroller, digital signalprocessor, or general purpose computer), programmable logic for use witha programmable logic device, (e.g., a Field Programmable Gate Array(FPGA) or other PLD), discrete components, integrated circuitry (e.g.,an Application Specific Integrated Circuit (ASIC)), or any other meansincluding any combination thereof. In a typical embodiment of thepresent invention, some or all of the processing of the sensor datacollected is implemented as a set of instructions or signals that areprocessed by a computer, circuit, processor, board, or other electronicdevice.

Programmable logic suitable for implementing overinsolation control maybe fixed either permanently or transitorily in a tangible storagemedium, such as a semiconductor memory device (e.g., a RAM, ROM, PROM,EEPROM, or Flash-Programmable RAM), a magnetic memory device (e.g., adiskette or fixed disk), an optical memory device (e.g., a CD-ROM), orother memory device. The programmable logic may be fixed in a signalthat is transmittable to a computer using any of various communicationtechnologies, including, but in no way limited to, analog technologies,digital technologies, optical technologies, wireless technologies (e.g.,Bluetooth), networking technologies, and internetworking technologies.Computers and computer systems described herein may include operativelyassociated computer-readable media such as memory for storing softwareapplications used in obtaining, processing, storing and/or communicatingdata. It can be appreciated that such memory can be internal, external,remote or local with respect to its operatively associated computer orcomputer system.

Memory may also include any means for storing software or otherinstructions including, for example and without limitation, a hard disk,an optical disk, floppy disk, DVD (digital versatile disc), CD (compactdisc), memory stick, flash memory, ROM (read only memory), RAM (randomaccess memory), DRAM (dynamic random access memory), PROM (programmableROM). EEPROM (extended erasable PROM), and/or other likecomputer-readable media.

In general, computer-readable memory media applied in association withembodiments of the invention described herein may include any memorymedium capable of storing instructions executed by a programmableapparatus. Where applicable, method steps described herein may beembodied or executed as instructions stored on a computer-readablememory medium or memory media. These instructions may be softwareembodied in various programming languages such as C++, C, Java, and/or avariety of other kinds of software programming languages that may beapplied to create instructions in accordance with embodiments of theinvention.

Vibration Control

The free piston Stirling engine operation is based on moving componentsoperating with no direct rigid mechanical connection between each other.Each moving part is equivalent to a mass in a system of masses that arelinked to each other via gas or springs. There are different componentswithin the energy generating apparatus and the Stirling engine, and allthe components interact as they move to contribute to the vibrations ofthe system (receiver, pistons, engine, and balancer). Avoiding thisinteraction is one purpose of an isolation suspension system.

As shown in various figures, such as FIG. 18A, in one preferredembodiment, a balancer 64 in communication with the engine housing 57reduces vibration caused by the internal components. In one embodiment,the balancer 64 is a passive balancer. Typically, this balancer 64 is apassive balancer in that it undergoes oscillation in response to otherinitiating forces within the energy converting apparatus. Balancers suchas passive balancers are well known in the art. See, e.g., U.S. Pat. No.5,895,033. The receiver portion 56, engine housing 57, and balancer 64are supported by a ring frame 66. Various aligned and coupled masseswithin the energy converting apparatus are maintained in alignment whilesuspended by the ring frame 66. For example, various subsystems such asthe receiver portion 56, engine portion 54, and passive balancer 64 areall supported and aligned by isolation springs 850, 850′, which attachto the ring frame 66. As shown in FIG. 18C, the ring frame has aplurality of supporting members 860 onto which a structural supportingring or loop is attached with various holes 858 and attachment points.

In accordance with one embodiment, the passive balancer is a subsystemfor counterbalancing vibrations of the energy converting apparatus.Referring back to FIGS. 2A and 2B, in one embodiment, the passivebalancer 64 is in mechanical communication with the engine housing 57via support member 67. The engine housing 57 in turn is carried byflexure assembly 856, which is connected to the ring frame 66 (FIG.18A). The flexure assembly 856 is in the form of at least one flatspring 850 including connections along a central portion 852. In oneembodiment, the geometry of the flexure spring 850 used can include aplurality of springs as shown in FIG. 18A. The central portion 852 ofeach spring is fixedly mounted to the ring frame support mount 860, andan outer peripheral portion 853 of the flat flexure spring 850 isfixedly mounted to support member 857. The flexure assembly 856functions, in part, as an isolation suspension that allows the engine 55and engine housing 57 to move relative to the ring frame 66 to reducethe amount of vibration transmitted to the ring frame 66. This springcompliance isolates a great deal of the force created within the energyconverter 54 from being fully transmitted to the ring frame 66. Thepassive balancer 64 resonantly responds to base motion of engine portion54 in order to provide further force cancellation to the internal forcesof the engine portion 54. Thus, in one embodiment, the flexure assembly856 and balancer 64 act together to minimize force transmitted to ringframe 66.

As shown in FIG. 18A, a heater head or heater plate element 102 receivesor absorbs solar radiation, which is first focused toward and then whichdiverges at or near the aperture. In one embodiment, two isolation platesprings 850, 850′ or flexures mount to a portion of the engine 55 or itshousing 57 to reduce vibrations on the engine side of the energyconverting apparatus. These isolation springs maintain the engine'scylindrical axis concentric to the axis of the ring frame 66, and theseisolation springs 850, 850′ provide a tailored axial compliance to keepthe heater head 102 within an anticipated range of collector enginemotions. The isolation spring's compliance reduces the dynamic vibrationload transmitted to the ring frame 66. Additional details relating to aconstituent element of the isolation spring are shown in FIG. 18B. Inone embodiment, the ring frame is selected such that the structuralvibration modes of this component is different from vibrationfrequencies created by the Stirling engine used in embodiments of theenergy converting apparatus.

The isolation springs 850, 850′ in FIG. 18B mount the engine to the ringframe 66. Holes 854 in the isolation springs 850, 850′ allow theisolation springs to orient relative to holes 858 in the support mounts860 of ring frame 66. The geometry of the springs 850, 850′ results insprings which are compliant in the axial direction while also beingrelatively very stiff in the radial and circumferential directions ofthe ring frame's cylindrical coordinate reference system. Referring toFIG. 18A, the ability of the springs 850, 850′ to flex reduces thetransmission of vibrations between the engine 55 or its housing 57 andthe ring frame 66. The two isolation springs 850, 850′ are shown mountedto a ring frame 66, which is a portion of the frame upon which the outercover is attached.

In one embodiment, a single isolation spring 850 includes individualspring plates. The two spring assemblies separate to provide a forcecouple to resist any rotation of the engine off the ring frame centralaxis. As shown in this embodiment, there are six spring plates, three ofwhich are combined together in a plane, forming a complete ring thatdefines one isolation spring 850. FIGS. 18C and 18D show additionaldetails relating to the ring frame 66. In one embodiment, the ring frame66 is a single piece of cast aluminum or is machined from a single pieceof aluminum. The ring frame 66 can also be cast, stamped, or machined asseparate components, which are joined together. The ring frame 66 formsa plurality of support mounts 860, which are evenly spaced around thering frame 66 and serve as attachment points for the isolation springs850. Isolation springs 850 can be mounted on both sides of the ringframe 66, (see FIG. 2B). The ring frame support mounts 860 can include aplurality of holes 858 for attaching the isolation springs 850. FIGS.19A, 19B and 19C show additional details relating to the frame. In oneembodiment, the ring frame is about 150 mm to about 160 mm long, about500 mm to about 510 mm high, about 400 mm to about 410 mm wide, and isabout 350 mm in diameter at the outer mounting bolt circle.

In one embodiment, the engine mounting and suspension system includes aring-shaped ring frame 66 and substantially planar springs 850, 850′.The angle that the clamp line makes relative to the flexure arm geometryis intended to be normal to the vector of maximum principal stress. Themounting is designed to be a high precision and inexpensivelymass-producible component with a service life as long as 75,000 hours.

The passive balancer 64 is engineered to minimize transmitted load tothe ring frame 66 within the tolerances and constraints of the engineoperating conditions. The balancer 64 resonates near the operatingfrequency and can reduce or partially-balance the fundamental frequencyvibration force of the energy converting apparatus or a subsystem ormass disposed therein. In one embodiment, the passive balancer operatesto reduce the transmission of vibration load to the ring frame thatwould otherwise occur because of free piston oscillations.

The springs flex due to gravity loads from orientation of theconcentrator during the day, and the springs flex in response to axialvibration forces that occur due to operation of the Stirling. Thegravity load is one constraint that can be addressed by increasing theaxial spring stiffness to ensure the heater head stays in the desiredaxial tolerance band. In one embodiment, this tolerance band ranges fromabout 0 mm to about 3 mm. In turn, the axial vibration forces determinehow much balancer force is needed to protect the remainder of theconcentrator from damage due to high-cycle fatigue due to enginevibration.

In general, the embodiments of the invention reduce the transmission ofvibrations from vibrating subsystems, such as the engine assembly bydetermining the appropriate mounting, balancing, and suspensionconditions: Maintaining the transmitted force from the engine to theconcentrator structure at or below an acceptable level allows the systemto reach reliability, performance, and product cost targets.

In part, the inclusion of a collinear suspended arrangement of masses inthe form of a receiver portion 56, engine portion 54, and passivebalancer 64 helps reduce transmission of unwanted vibrations and forces.Thus, in one embodiment, elements of the energy converting apparatusoperate as a multiple degree of freedom resonant system (i.e., piston,displacer, engine housing, and balancer.) In one embodiment, the boomand the ring frame can also provide additional degrees of freedom. Themounting or frame of the casing (or engine housing) 57, which includesthe engine, provides one degree of freedom. The engine housing respondsto forces from the power piston, which causes the alternator to move,and the displacer (that displaces fluid in the machine) (107 in FIGS. 2Band 2C) and the passive balancer (each with its own degree of freedom)to provide a total of four degrees of freedom. This mounting or ringframe and isolation suspension provide further reaction forces to thehousing. These various elements, which vibrate while suspended byflexures in the ring frame, represent a tunable mass system. In oneembodiment, this suspend mass system can be tuned to meet variousdynamic constraints. In one specific embodiment, the constraint is tolimit the range of dynamic axial movement (or predetermined axialtolerance band) from about 0.1 mm to about 0.6 mm with respect to afixed reference point, such as the ring frame, for a total range ofabout 1.2 mm. In one preferred embodiment, the axial constraint inmovement (such as an axial deflection of the engine housing measuredrelative to the ring frame) is about 0.3 mm, for a total range of about0.6 mm. Thus, in one embodiment, a predetermined axial tolerance bandranges from about 0 min to about 0.3 mm in one embodiment. Further, inanother embodiment a predetermined axial tolerance band range from about0 mm to about 0.6 mm.

This system of masses, a frame, and flexures has a distinct advantageover other mounting approaches. For example, the flexures on the ringframe allow the engine to be positioned relative to the sun whileremaining constrained within the ring frame inside the energy convertingapparatus. Coil springs have no lateral stiffness and are not suitableto meet the goal of this suspension without other features for lateralmotion control. The lateral stiffness of the flexures keeps the energyconverting apparatus internal subsystems substantially fixed when movingthe apparatus and tracking the sun. In addition, the lateral stiffnessmaintains the location of the ECA when it is subjected to gravitationalloads from different orientations during device operation.

Heater Head/Heat Exchanger

As shown in FIG. 20, the heat exchanger 102 (alternatively heater plate,flat hot heat exchanger (FHHX), or heater head) is a novel multi platebrazement that includes a manifold 954, manifold plate 962, channelplate 964, and top plate 968 in one embodiment. The heater head 102shown in FIG. 20 receives the solar radiation or other heat to begin theengine's Stirling cycle. The material selection of the components isimportant in balancing the operating pressure, operating temperature,longevity, and cost. The architecture of this component allows for theeasy adaptation of the Stirling engine, of which it is a component, toany potential heat source, including solar, bio gas, radioisotope,diesel fuel, natural gas, etc.

The multi-plate brazement architecture helps create a heat absorbersurface ideally suited to long-life, mass-producible, multi-market, heatexchanger components. The heat exchanger 102 transfers thermal powerfrom the absorber surface 968 to the engine working fluid via convectiveheat transfer. The desire to have a high fluid velocity needed to assuresufficient heat exchange must be tempered with minimizing the fluidicback pressure associated with internal tubular flow. The optimization ofchannel geometry within the one-piece channel plate assures excellentheat transfer with a minimum of flow losses while adequately coveringthe entire absorbing surface, negating heat transfer dead zones.

In various embodiments of the present teachings, the heater head 102(see FIG. 18A) interfaces with a heat engine, such as, for example, aStirling engine 55. The heater head 102 transfers thermal energy from aheat source to the heat engine 55. The heater head 102 can interfacewith any suitable heat source, such as, for example, heat generated fromsolar energy and/or a combustion burner (e.g., a JP-8 diesel burner).

Referring to FIG. 20, in various embodiments, the heater head can beformed from a plurality of components. The components can include a topplate 968, a channel plate 964, a flow distributor 962, a cold sideflange 958, a manifold block 954, a heater head wall 952, and adisplacement cylinder 950. In some embodiments, the individualcomponents can be joined to form an integral heater head such as thatdepicted in FIGS. 21A-C.

In some embodiments, the heater head can be formed from a plurality ofcomponents that can include one or more sacrificial plates. One or moresacrificial plates can be interpolated between any or all of thecomponents which form the heater head. For example, one or moresacrificial layers can be interpolated between the top plate and thechannel plate, one or more sacrificial layers can be interpolatedbetween the channel plate and flow distribution plate, and/or one ormore sacrificial layers can be interpolated between the flowdistribution plate and the manifold block.

The sacrificial layers can be composed of any suitable low-melting pointmaterial or materials, such as a metal alloy. In some embodiments, theindividual components can be joined together to form an integral heaterhead, such as that depicted in FIGS. 21A-C, while the sacrificial layersare substantially converted into platelets or tubes that allow heatexchange through the holes and channels in the final brazed heater headassembly. The sacrificial layers typically include a low melting pointmetal that liquefies during in the brazing process.

The components of the heater head can be composed of any suitablematerial that can withstand high thermal temperatures and large thermalgradients in long life design applications. In various embodiments, thetop plate, channel plate, flow distribution plate, manifold block,heater head wall, cold side flange, and displacement cylinder are madefrom solution annealed Inconel® 625 or Haynes® 230 alloys. Thisparticular material choice can be made from a class of metals calledsuper-alloys, high thermal-performance alloys, or any other descriptorof a metal that is designed or is innately inclined to have appropriatestructural and heat-transfer performance at a high temperature. In someembodiments, the cold side flange is made from a 300 series stainlesssteel, such as 304, for ease of machining. One of skill in the art willappreciate that many other suitable materials can be used in accordancewith the present teachings.

The heater head can include two major subassemblies, a pressure vesselsubassembly and a hot heat exchange subassembly. The pressure vesselsubassembly can include the cold side flange, heater head wall,displacer cylinder, and manifold block.

The manifold block acts as an end cap for the pressure vesselsubassembly. The manifold block is substantially torispherical in shape.The top of the manifold (i.e., the surface which faces the hot heatexchanger) can include an asymmetric hub which facilitates alignment ofthe manifold block, the flow distributor plate, the channel plate,and/or the top plate. The central hub can have one or more asymmetricnotches that are positioned such that it is impossible to align theplates incorrectly. The manifold block can be roughly sized using theASME boiler and pressure vessel code and then refined using finiteelement analysis (FEA) modeling. In some embodiments, the manifold blockcontains porting features to allow for the communication of heliumbetween the expansion space and the compression space by way of the hotheat exchanger. The manifold block can be formed by, for example,machining or investment casting.

Referring to FIG. 22, the heater head wall profile is optimized forstructural efficiency and thermal loss reduction. The heater head wall952 can have a tailored wall profile. The heater head wall can be madefrom Inconel® 625 or Haynes® 230 by, for example, a flow forming processor by machining. This particular material choice can be made from aclass of metals called super-alloys, high thermal-performance alloys, orany other descriptor of a metal that is designed or is innately inclinedto have appropriate structural and heat-transfer performance at a hightemperature. The heater head wall can be welded to the manifold blockusing a laser weld or other suitable welding process. A brazing processis also acceptable.

Referring to FIG. 20, in some embodiments, the cold side flange 958provides a mount on the heater head for the heat engine. The cold sideflange can be a substantially planar ring. The cold side flange can alsohave a plurality of holes for reversibly attaching the heater head tothe heat engine using, for example, screws or bolts. The cold sideflange can be joined to the heater head wall using a braze joint, suchas an annular seat located on the inside diameter of the cold sideflange, which scat is configured to receive the heat head wall. In otherembodiments, the cold side flange can be replaced with a bimetallicjoint from the aluminum engine housing to the Inconel® heater head. Thecold side flange can be milled from either a plate or a casting.

Referring to FIG. 20, the displacer cylinder 900 is a thin-walledstructure and is used to create the annular cavities which form anexpansion space and a regenerator space. In various embodiments, thedisplacer cylinder 900 is made of Inconel® 625 or Haynes® 230, tominimize stresses caused by differential thermal expansion, which couldoccur if other materials were used. This particular material choice canbe made from a class of metals called super-alloys, highthermal-performance alloys, or any other descriptor of a metal that isdesigned or is innately inclined to have appropriate structural andheat-transfer performance at a high temperature. The cylinder can berolled and welded from sheet material and/or can be machined, drawn orflow formed. The cylinder can be brazed into the manifold block.

The second major subassembly of the heater head is the hot heatexchanger (HHX). In some embodiments, the hot heat exchanger subassemblyis formed from three different plates that, when joined, form the heliumflow passages. The three plates include the top plate 968, the channelplate 964, and the flow distribution plate 962, each of which can bemade of Inconel® 625 or Haynes® 230. This particular material choice canbe made from a class of metals called super-alloys, highthermal-performance alloys, or any other descriptor of a metal that isdesigned or is innately inclined to have appropriate structural andheat-transfer performance at a high temperature.

In various embodiments, the top plate is the heat-absorbing surface ofthe hot heat exchanger. The top plate can be substantially disc shapedand/or can be substantially planar. The top plate can have a locatingfeature in the center of the plate, which receives the central hub ofmanifold plate, and thereby facilitates alignment of the top plate withthe manifold block, the flow distribution plate, and/or the channelplate. In some embodiments, the locating feature can include one or moreasymmetric tabs, which are configured to interact with one or moreasymmetric notches in the central hub such that the plates cannot bealigned incorrectly.

The top plate can be, for example, between about 0.1 and about 0.001inches thick and, more preferably, between about 0.050 and about 0.01inches thick. In some embodiments, the top plate is about 0.040 inchesin thickness. The plate can be formed by stamping or machining. Inembodiments where the heater head is used with a combustion burner,metal fins can be used as extended surface area to enhance heat transferbetween the top plate and the combustion burner. The heat exchanger finscan be formed from sheet metal or can be cast or machined.

Referring to FIG. 23, in various embodiments, the channel plate 964contains a plurality of arcuate finned channels which radiate from thecentral region of the channel plate. The channels both expand theavailable surface area on the helium side of the heat exchanger anddirect helium flow across the top plate surface. Channels may bestaggered in location allowing for the entire absorbing surface toparticipate in active heat transfer. The shape of the finned channelscan be a substantially elongated S-shape, which shape provides fornormal entry into the inside diameter plenum space of the manifold blockand the turnaround plenum in the distribution plate, thereby reducingflow losses in those regions.

The channel plate can be substantially disc shaped and/or can besubstantially planar. The channel plate can have a locating feature inthe center of the plate, which receives the central hub of manifoldplate, and thereby facilitates alignment of the channel plate with themanifold block, the flow distribution plate, and/or the top plate. Insome embodiments, the locating feature can include one or moreasymmetric tabs, which are configured to interact with one or moreasymmetric notches in the central hub such that the plates cannot bealigned incorrectly. The channel plate can be, for example, betweenabout 0.5 and about 0.01 inches thick and, more preferably, betweenabout 0.25 and about 0.1 inches thick. In some embodiments, the channelplate is about 0.187 inches in thickness. The channel plate can belaser-cut from sheet material.

The flow distribution plate distributes helium flow from the manifoldplenums and through each of the finned channels of the channel plate.Referring to FIG. 24, the flow distribution plate 962 can have aplurality of holes arranged in substantially concentric circles aroundthe center of the plate. In some embodiments, the flow distributionplate can have a turnaround plenum on the outside diameter of the plate.The turnaround plenum functions to transfer helium from the finnedchannel connecting the inside diameter manifold plenum to the outsidediameter of the absorber, to the channel connecting the outside diameterof the absorber to the outside diameter manifold plenum. In this way,the fins in the channel plate are able to be supported at both theinside diameter and outside diameter of the channel plate, therebymaking the channel plate easier to manufacture. The flow distributionplate can be substantially disc shaped and/or can be substantiallyplanar.

The flow distribution plate can have a locating feature in the center ofthe plate, which receives the central hub of manifold plate, and therebyfacilitates alignment of the flow distribution plate with the manifoldblock, the top plate, and/or the channel plate. In some embodiments, thelocating feature can include one or more asymmetric tabs, which areconfigured to interact with one or more asymmetric notches in thecentral hub such that the plates cannot be aligned incorrectly. The flowdistribution plate can be, for example, between about 0.5 and about0.001 inches thick and, more preferably, between about 0.25 and about0.01 inches thick. In some embodiments, the flow distribution plate isabout 0.030 inches in thickness.

The components of the heater head can be joined together using one weldand a single inert gas belt braze. In some embodiments, the heater headwall is first welded to the manifold block. The weld can be accomplishedby, for example, a single sided, butt-joint, laser weld with a backingplate. Once the manifold block and heat head wall are welded, theremaining components can be stacked and readied for the braze process.In various embodiments, the top plate, the channel plate, and the flowdistributor plate can be aligned to the manifold block using a centralhub located on the top of the manifold block.

The central hub can have one or more asymmetric notches that arepositioned such that it is impossible to align the plates incorrectly. Asolid ring braze alloy pre-form is placed between each component andcovers all surfaces to be brazed. Excess braze may coat the helium flowchannels, but will be insufficient to cause blockages. The braze alloypre-forms can have tabs on their outside diameter that protrude past theoutside diameter of the hot heat exchanger to give visual confirmationthat braze alloy pre-forms have been inserted. The cold side flange andthe displacer cylinder can be fixtured to allow proper alignment withthe engine cylinder. Braze paste can be manually applied to each ofthese parts in some embodiments. Visual post-braze inspection willinsure that proper wetting of the alloy has occurred.

Any suitable braze alloy can be used to braze the heater head componentstogether. The braze alloy can be, for example, a copper, Nicrobraz® 51,or gold-based alloy. Copper is particularly suitable as a braze alloy,as it can be used in the form of a clad sheet, which avoids the expenseof placing braze alloy pre-forms between the plates of the hot heatexchanger.

The manifold block is configured to divorce the structural requirementsof the pressure vessel from the heat transfer requirements of the hotheat exchanger. By minimizing the contact surfaces between the manifoldblock and the hot heat exchanger, the hot heat exchanger is allowedgreater freedom to grow and relieve stresses built up by thermalexpansion. A further advantage is a reduction in the amount of stressimposed on the top plate of the hot heat exchanger by the deformation ofthe manifold block.

In some embodiments, the duty life of the heater head exceeds 60,000hours. In various embodiments, the heater head can tolerate internalpressures of up to about 1000 psig peak. In addition, the heater headcan tolerate a maximum hot side temperature of about 825° C.,corresponding to a cold side temperature of about 87° C. (rejectiontemperature), in various embodiments.

The methods and systems described herein can be performed in software ongeneral purpose computers, servers, or other processors, withappropriate magnetic, optical or other storage that is part of thecomputer or server or connected thereto, such as with a bus. Theprocesses can also be carried out in whole or in part in a combinationof hardware and software, such as with application specific integratedcircuits. The software can be stored in one or more computers, servers,or other appropriate devices, and can also be kept on a removablestorage media, such as a magnetic or optical disks.

Subsystems and Other Embodiments

In part, there are certain hardware and software implementations thatenhance device operation and safety. One such approach uses data fromthe receiver assembly to calibrate and commence device operation afterinstallation. This auto-commissioning process helps the energyconverting apparatus locate the sun. Auto-commissioning is a way toautomatically predict where the receiver aperture is located withoutuser interaction. This is accomplished by using the sensors on the slewcone to determine the location of the aperture (any sensor locatedanywhere may be able to accomplish this). Auto-commissioning enables alarge field of systems to be aligned with respect to the sun without auser observing where the concentrated solar energy is located whenlocating the sun. The method of auto-commissioning observes when thereceiver temperature sensors rise in temperature while passing theconcentrated solar energy over the front of the system. The system makesa plurality of vertical or horizontal passes (or both) to collect thenecessary data.

Various exemplary parameters relating to system, method, and deviceembodiments are provided below. These examples are not meant to limitthe scope of the invention, but only to provide details relating tocertain embodiments.

Ambient Design Exemplary Parameters (Non-Limiting Example)

-   -   Operating temperature range=about −20° C. to about +55° C.        (about −4° F. to about 131° F.)    -   Operating elevation range=up to about 1,890 m (about 6,200 feet)        above sea level    -   Operating humidity level=0 to 100%    -   Wind speed (maximum)=about 100 mph    -   Snow load (maximum, stowed)*=about 1 kN/m2 (20.9 pfs) on        inverted dish    -   Ice load (maximum, stowed)*=about 5.0 cm (1.97″) on one side

Exemplary System Parameters (Non-Limiting Example)

-   -   Focal Length: about 2.68 m    -   Aperture Diameter: about 95 mm    -   Absorber & receiver wall temperature: about 700° C.    -   Ambient temperature: about 25° C.    -   Receiver insulation thermal conductivity: about 0.06 W/m−K    -   Receiver efficiency: about 90%    -   Thermal power into receiver: about 10,000 W    -   45 degree angle should be assumed for the cover diameter away        from the aperture    -   about 8,000 kW/m2 peak at 2.68 m focal length, about 1,000 kW/m2        peak at 2.56 m (use linear correlation)

In the description, the invention is discussed in the context ofStirling engines; however, these embodiments are not intended to belimiting and those skilled in the art will appreciate that the inventioncan also be used for many types of energy converting systems includingmulti-cylinder engines, whether Stirling cycle based or otherwise,kinematic engines, steam and water based solar energy converting andstorages systems, and other types of energy converting apparatus whereinuseful work or electricity is produced.

It should be appreciated that various aspects of the claimed inventionare directed to subsets and substeps of the techniques disclosed herein.Further, the terms and expressions employed herein are used as terms ofdescription and not of limitation, and there is no intention, in the useof such terms and expressions, of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed. Accordingly, what is desired to be secured by LettersPatent is the invention as defined and differentiated in the followingclaims, including all equivalents.

What is claimed is:
 1. A method for reducing over-insolation of a heatexchanger, the method comprising the steps of: providing a heatexchanger having a surface area for absorbing solar radiation;concentrating solar radiation on the surface area of the heat exchangersuch that the concentrated solar radiation impinges on a portion of theentire surface area of the heat exchanger; and moving the concentratedsolar radiation about the surface area of the heat exchanger in asubstantially circular pattern at about 1 to about 30 revolutions perminute.
 2. A method for reducing over-insolation of a heat exchanger,the method comprising the steps of: providing a heat exchanger having asurface area for absorbing solar radiation; concentrating solarradiation on the surface area of the heat exchanger such that theconcentrated solar radiation impinges on a portion of the entire surfacearea of the heat exchanger; and moving the concentrated solar radiationabout the surface area of the heat exchanger in a randomized movement ofthe concentrated solar radiation.
 3. A method for reducingover-insolation of a heat exchanger, the method comprising the steps of:providing a heat exchanger having a surface area for absorbing solarradiation; concentrating solar radiation on the surface area of the heatexchanger such that the concentrated solar radiation impinges on aportion of the entire surface area of the heat exchanger; moving theconcentrated solar radiation about the surface area of the heatexchanger in a pattern; and reducing the portion of the surface areaonto which concentrated solar radiation impinges when the temperature ofthe heat exchanger reaches a predetermined limit, thereby reducingthermal input.
 4. A method for reducing over-insolation of a heatexchanger, the method comprising the steps of: providing a heatexchanger having a surface area for absorbing solar radiation;concentrating solar radiation on the surface area of the heat exchangersuch that the concentrated solar radiation impinges on a portion of theentire surface area of the heat exchanger; moving the concentrated solarradiation about the surface area of the heat exchanger in a pattern; andreducing the portion of the surface area onto which concentrated solarradiation impinges when the temperature of the heat exchanger reaches apredetermined limit, thereby reducing thermal input, wherein the heatexchanger is in thermal communication with an energy convertingapparatus, the energy converting apparatus selected from the groupconsisting of a Stirling engine, chemical energy conversion device, athermal energy storage device, a gas turbine, a multi-cylinder engine, amulti-piston engine, a steam turbine, a steam power tower, a fuel cell,and a water-based energy generation systems.
 5. A method for reducingover-insolation of a heat exchanger, the method comprising the steps of:providing a solar concentrator; providing a Stirling engine; providing aheat exchanger having a surface area, the heat exchanger being inthermal communication with the Stirling engine; providing an aperturebetween the heat exchanger and the solar concentrator; aligning thesolar concentrator and the aperture such that a fraction of the solarradiation from the solar concentrator passes through the aperture,wherein the fraction of solar radiation impinges on a portion of thesurface area of the heat exchanger; and moving the solar radiation aboutthe surface area of the heat exchanger.
 6. The method of claim 5,comprising the step of reducing the portion of the surface area ontowhich concentrated solar radiation impinges when the temperature of theheat exchanger reaches a predetermined limit, thereby reducing thermalinput.
 7. The method of claim 6, comprising the step of moving theconcentrated solar radiation such that substantially no concentratedsolar radiation impinges on the heat exchanger when a predeterminedmaximum temperature, power, pressure, swept volume, resistance, current,or position, is reached.
 8. The method of claim 5, further comprisingthe steps of during non-peak solar conditions, directing most of thesolar radiation from the solar concentrator through an electromagneticradiation path; and during peak solar conditions, reducing the amount ofsolar radiation which passes through the electromagnetic radiation pathand moving the solar radiation about the surface area of the heatexchanger, thereby reducing thermal input, spreading hot spots, reducingthe rate at which the heat exchanger heats, and/or maintaining coolanttemperature.
 9. The method of claim 5, further comprising the step ofwhen the heat exchanger reaches a predetermined temperature limit,reducing the amount of solar radiation which passes through theaperture, thereby reducing the amount of solar radiation impinging onthe heat exchanger.
 10. The method of claim 9, wherein the step ofreducing the amount of solar radiation comprises misaligning the solarconcentrator and the aperture.